remove parasail, use biopython

[tlambert03]

biopython is slower, but parasail is unmaintained... this is not urgent. #267 tests the functionality

[codecov]

Codecov Report

❌ Patch coverage is 85.10638% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.16%. Comparing base (ff170c9) to head (e53521b).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
backend/fpseq/align.py	84.78%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #266      +/-   ##
==========================================
- Coverage   50.43%   50.16%   -0.28%     
==========================================
  Files         111      111              
  Lines        9555     9585      +30     
==========================================
- Hits         4819     4808      -11     
- Misses       4736     4777      +41     

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