tests: Fix version picking in toxgen

[sentrivana]

Toxgen should only consider the highest patch release of each major.minor version. For the most part this was working fine as long as the releases were ordered as expected in PyPI, but in cases where a lower patch version succeeded a higher patch version in the release list from PyPI, we would incorrectly consider the lower patch version as well, instead of ignoring it in favor of the higher patch.

Example:

• we pull releases [1.2.3, 1.2.4, 1.2.5, 1.2.2] from PyPI (in that order)
• we consolidate 1.2.3, 1.2.4, 1.2.5 into one version, 1.2.5, as expected
• 1.2.2 will not disappear into 1.2.5 because of a faulty check in toxgen and will instead be considered as a new version
• our resulting list of releases eligible for testing will be [1.2.5, 1.2.2] instead of just [1.2.5], which then results in picking versions that are not nicely spaced apart

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.30%. Comparing base (b96e2b6) to head (e01978a).
Report is 1 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4323      +/-   ##
==========================================
- Coverage   80.31%   80.30%   -0.01%     
==========================================
  Files         142      142              
  Lines       15930    15930              
  Branches     2725     2725              
==========================================
- Hits        12794    12793       -1     
  Misses       2262     2262              
- Partials      874      875       +1     

see 1 file with indirect coverage changes

[antonpirker]

looks good