set defaults for lr sinkhorn

[MUCDK]

No description provided.

[MUCDK]

resolves #705

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 77.04%. Comparing base (f940c18) to head (2bbcd55).
Report is 175 commits behind head on main.

Files with missing lines	Patch %	Lines
src/moscot/backends/ott/solver.py	75.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #739      +/-   ##
==========================================
- Coverage   78.14%   77.04%   -1.10%     
==========================================
  Files          36       36              
  Lines        3834     4370     +536     
  Branches      705      807     +102     
==========================================
+ Hits         2996     3367     +371     
- Misses        526      651     +125     
- Partials      312      352      +40     

Files with missing lines	Coverage Δ
src/moscot/backends/ott/solver.py	90.25% <75.00%> (-1.32%)	⬇️

... and 3 files with indirect coverage changes

[selmanozleyen]

I'd think we should document the default gamma somewhere but it shouldn't matter as we are going to remove kwargs from the solve method in the future. So gamma can be explicitly documented there