Update branches from master to main for ReCirq and qsim

[mhucka]

This updates default branch names in a couple of references to the ReCirq and qsim repositories on GitHub.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.37%. Comparing base (3317377) to head (0f93659).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7689      +/-   ##
==========================================
- Coverage   99.38%   99.37%   -0.01%     
==========================================
  Files        1089     1089              
  Lines       97414    97414              
==========================================
- Hits        96812    96807       -5     
- Misses        602      607       +5     

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