Pin sphinx<7.2.0 to avoid doc build failure.

[moorepants]

References to other Issues or PRs

Temporarily fixes #25541

Brief description of what is fixed or changed

Sphinx 7.2.0 came out today and our documentation build (make html) fails with this version. This fix should let CI pass until we get it working with version 7.2.0.

Other comments

Release Notes

NO ENTRY

[sympy-bot]

✅

Hi, I am the SymPy bot. I'm here to help you write a release notes entry. Please read the guide on how to write release notes.

• No release notes entry will be added for this pull request.

Click here to see the pull request description that was parsed.

<!-- Your title above should be a short description of what
was changed. Do not include the issue number in the title. -->

#### References to other Issues or PRs
<!-- If this pull request fixes an issue, write "Fixes #NNNN" in that exact
format, e.g. "Fixes #1234" (see
https://tinyurl.com/auto-closing for more information). Also, please
write a comment on that issue linking back to this pull request once it is
open. -->

Temporarily fixes https://github.com/sympy/sympy/issues/25541

#### Brief description of what is fixed or changed

Sphinx 7.2.0 came out today and our documentation build (`make html`) fails with this version. This fix should let CI pass until we get it working with version 7.2.0.

#### Other comments


#### Release Notes

<!-- Write the release notes for this release below between the BEGIN and END
statements. The basic format is a bulleted list with the name of the subpackage
and the release note for this PR. For example:

* solvers
  * Added a new solver for logarithmic equations.

* functions
  * Fixed a bug with log of integers. Formerly, `log(-x)` incorrectly gave `-log(x)`.

* physics.units
  * Corrected a semantical error in the conversion between volt and statvolt which
    reported the volt as being larger than the statvolt.

or if no release note(s) should be included use:

NO ENTRY

See https://github.com/sympy/sympy/wiki/Writing-Release-Notes for more
information on how to write release notes. The bot will check your release
notes automatically to see if they are formatted correctly. -->

<!-- BEGIN RELEASE NOTES -->
NO ENTRY
<!-- END RELEASE NOTES -->

[github-actions]

Benchmark results from GitHub Actions

Lower numbers are good, higher numbers are bad. A ratio less than 1
means a speed up and greater than 1 means a slowdown. Green lines
beginning with + are slowdowns (the PR is slower then master or
master is slower than the previous release). Red lines beginning
with - are speedups.

Significantly changed benchmark results (PR vs master)

Significantly changed benchmark results (master vs previous release)

       before           after         ratio
     [8059df73]       [f0605682]
     <sympy-1.12^0>                 
-        85.6±2ms       55.4±0.5ms     0.65  integrate.TimeIntegrationRisch02.time_doit(10)
-      83.4±0.4ms       54.6±0.6ms     0.65  integrate.TimeIntegrationRisch02.time_doit_risch(10)
-     6.90±0.01ms         3.66±0ms     0.53  logic.LogicSuite.time_load_file
-     2.11±0.01ms          620±1μs     0.29  polys.TimePREM_LinearDenseQuadraticGCD.time_op(3, 'sparse')
-     10.4±0.04ms      1.86±0.01ms     0.18  polys.TimePREM_LinearDenseQuadraticGCD.time_op(5, 'sparse')
-         364±1μs       77.9±0.3μs     0.21  polys.TimePREM_QuadraticNonMonicGCD.time_op(1, 'sparse')
-     4.71±0.01ms          343±1μs     0.07  polys.TimePREM_QuadraticNonMonicGCD.time_op(3, 'sparse')
-     10.6±0.02ms      1.04±0.01ms     0.10  polys.TimePREM_QuadraticNonMonicGCD.time_op(5, 'sparse')
-     6.26±0.01ms      3.80±0.01ms     0.61  polys.TimeSUBRESULTANTS_LinearDenseQuadraticGCD.time_op(2, 'sparse')
-     27.5±0.04ms      11.5±0.02ms     0.42  polys.TimeSUBRESULTANTS_LinearDenseQuadraticGCD.time_op(3, 'sparse')
-     6.72±0.01ms         1.11±0ms     0.17  polys.TimeSUBRESULTANTS_QuadraticNonMonicGCD.time_op(1, 'sparse')
-     15.8±0.06ms      8.91±0.02ms     0.56  polys.TimeSUBRESULTANTS_QuadraticNonMonicGCD.time_op(2, 'sparse')
-       205±0.2ms      67.9±0.06ms     0.33  polys.TimeSUBRESULTANTS_QuadraticNonMonicGCD.time_op(3, 'sparse')
-     6.35±0.01ms          504±1μs     0.08  polys.TimeSUBRESULTANTS_SparseGCDHighDegree.time_op(3, 'sparse')
-     27.2±0.05ms          801±1μs     0.03  polys.TimeSUBRESULTANTS_SparseGCDHighDegree.time_op(5, 'sparse')
-         594±1μs        200±0.8μs     0.34  polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(1, 'sparse')
-     6.34±0.03ms        205±0.8μs     0.03  polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(3, 'sparse')
-     16.5±0.06ms          207±1μs     0.01  polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(5, 'sparse')
-       162±0.9μs       91.3±0.3μs     0.56  solve.TimeMatrixOperations.time_rref(3, 0)
-       304±0.2μs          108±1μs     0.36  solve.TimeMatrixOperations.time_rref(4, 0)
-     29.8±0.08ms      12.8±0.05ms     0.43  solve.TimeSolveLinSys189x49.time_solve_lin_sys

Full benchmark results can be found as artifacts in GitHub Actions
(click on checks at the top of the PR).

[moorepants]

Is this possible it will fail on Sphinx < 7.2.0?

[oscarbenjamin]

Yes, I have just confirmed that locally.

[oscarbenjamin]

I've removed that commit

[oscarbenjamin]

Set to automerge. I'll open a followup PR to unpin the version.