chore: update CHANGELOG for v0.11.15

[pyansys-ci-bot]

Update CHANGELOG for v0.11.15 and remove .md files in doc/changelog.d.

Caution

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

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.00% (target: -1.00%)	✅ ∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (625adcd)	2537	2191	86.36%
Head commit (f1b3126)	2537 (+0)	2191 (+0)	86.36% (+0.00%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#1161)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.36%. Comparing base (625adcd) to head (f1b3126).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1161   +/-   ##
=======================================
  Coverage   86.36%   86.36%           
=======================================
  Files          39       39           
  Lines        2537     2537           
=======================================
  Hits         2191     2191           
  Misses        346      346           

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