fix: fruit fly RR genes

[joyceyan]

Reason for Change

• we received feedback from lattice here that some fruit fly genes start with RR

Changes

• updated the gencode mapper to account for this

Testing

• added fruit fly genes to valid_genes in test_gencode

Notes for Reviewer

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.64%. Comparing base (241cefd) to head (d6196b5).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1252   +/-   ##
=======================================
  Coverage   89.64%   89.64%           
=======================================
  Files          19       19           
  Lines        2222     2222           
=======================================
  Hits         1992     1992           
  Misses        230      230           

Components	Coverage Δ
cellxgene_schema_cli	90.48% <100.00%> (ø)
migration_assistant	91.26% <ø> (ø)
schema_bump_dry_run_genes	79.74% <ø> (ø)
schema_bump_dry_run_ontologies	99.53% <ø> (ø)