MAINT, REL: unpin Python 1.11.x branch (#19517)

* this patch against our latest maintenance branch is
related to gh-19513, and NumPy made a similar decision
upstream in numpy/numpy#24962

* the discussions surrounding this are pretty confusing,
but it seems like we may need to do it for resolvers
like those used by `poetry`...

* I suppose this increases the likelihood I have to do
`1.11.4`, but it was looking somewhat likely anyway...

[skip cirrus] [skip circle]

pyproject.toml

@@ -64,7 +64,7 @@ maintainers = [
 # Note: Python and NumPy upper version bounds should be set correctly in
 # release branches, see:
 #     https://scipy.github.io/devdocs/dev/core-dev/index.html#version-ranges-for-numpy-and-other-dependencies
-requires-python = ">=3.9,<3.13"
+requires-python = ">=3.9"
 dependencies = [
     "numpy>=1.21.6,<1.28.0",
 ]