Fix various bugs

[Marius1311]

• Removes tenacity for retries: openAI does this internally already
• Updated the license file
• fixes tests by adding some more marker genes
• adds rich to the test dependencies.

closes #25

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Project coverage is 85.80%. Comparing base (b9cab03) to head (998f82f).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
src/cell_annotator/utils.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #28      +/-   ##
==========================================
+ Coverage   85.77%   85.80%   +0.03%     
==========================================
  Files           9        9              
  Lines         450      451       +1     
==========================================
+ Hits          386      387       +1     
  Misses         64       64              

Files with missing lines	Coverage Δ
src/cell_annotator/_constants.py	100.00% <100.00%> (ø)
src/cell_annotator/base_annotator.py	100.00% <100.00%> (ø)
src/cell_annotator/cell_annotator.py	82.43% <100.00%> (ø)
src/cell_annotator/sample_annotator.py	84.84% <100.00%> (ø)
src/cell_annotator/utils.py	82.05% <0.00%> (ø)