CHORE: update CHANGELOG for v0.17.3

[pyansys-ci-bot]

Update CHANGELOG for v0.17.3 and remove .md files in doc/changelog.d.

Caution

Do not merge this pull request until the release has been successfully made.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.29%. Comparing base (d2c91c1) to head (e453150).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6297      +/-   ##
==========================================
- Coverage   85.30%   85.29%   -0.01%     
==========================================
  Files         173      173              
  Lines       65331    65331              
==========================================
- Hits        55728    55726       -2     
- Misses       9603     9605       +2     

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