Backport PR #4057 on branch 1.12.x (docs: add inline example plot to sc.pl.rank_genes_groups_stacked_violin)

[meeseeksmachine]

Backport PR #4057: docs: add inline example plot to sc.pl.rank_genes_groups_stacked_violin

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.47%. Comparing base (1fce8f6) to head (c587405).
⚠️ Report is 2 commits behind head on 1.12.x.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           1.12.x    #4068   +/-   ##
=======================================
  Coverage   78.47%   78.47%           
=======================================
  Files         119      119           
  Lines       12624    12624           
=======================================
  Hits         9907     9907           
  Misses       2717     2717           

Flag	Coverage Δ
hatch-test.low-vers	77.77% <ø> (ø)
hatch-test.pre	78.35% <ø> (ø)

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Files with missing lines	Coverage Δ
src/scanpy/plotting/_tools/__init__.py	77.02% <ø> (ø)