Update rstest dev-dependency from 0.23 to 0.26

[musicinmybrain]

I don’t see any changes that should affect this project between these two versions (https://github.com/la10736/rstest/blob/v0.26.1/CHANGELOG.md), and I confirmed that cargo test -p time --all-features still passes.

(I’m patching the dev-dependency in Fedora’s rust-time package to remove one of the dependencies on our rust-rstest0.23 compat package so we don’t have to maintain it indefinitely, and it’s our policy to offer patches upstream. See #716 for more discussion on motivation, although this PR should be more straightforward since it doesn’t affect MSRV.)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.4%. Comparing base (b6f27d6) to head (bce62e3).

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #747     +/-   ##
=======================================
- Coverage   92.4%   92.4%   -0.0%     
=======================================
  Files         95      95             
  Lines       9652    9652             
=======================================
- Hits        8922    8920      -2     
- Misses       730     732      +2     

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