Molmedb anotator index fix

[DominikMartinat]

Fixed issue with indexing of dataframe rows to drop in MolMeDB annotator
Changed MolMeDB gene example

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 12.17%. Comparing base (a2c406e) to head (a943088).
Report is 6 commits behind head on main.

Files	Patch %	Lines
src/pyBiodatafuse/annotators/molmedb.py	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #78      +/-   ##
==========================================
- Coverage   12.36%   12.17%   -0.19%     
==========================================
  Files          25       25              
  Lines        1189     1191       +2     
  Branches      222      223       +1     
==========================================
- Hits          147      145       -2     
- Misses       1040     1042       +2     
- Partials        2        4       +2     

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