Update ahash to 0.8.7 to accommodate stdsimd change in nightly

[dtolnay]

CI is impacted by tkaitchuck/aHash#200, which is fixed in ahash 0.8.7. I see the following in the jobs that ran on #694:

error[E0635]: unknown feature `stdsimd`
  --> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ahash-0.8.6/src/lib.rs:99:42
   |
99 | #![cfg_attr(feature = "stdsimd", feature(stdsimd))]
   |                                          ^^^^^^^

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1be8fa3) 65.41% compared to head (2b17850) 65.41%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #695   +/-   ##
=======================================
  Coverage   65.41%   65.41%           
=======================================
  Files          38       38           
  Lines        2322     2322           
=======================================
  Hits         1519     1519           
  Misses        803      803           

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