Remove rustworkx as a dependency

[oscarhiggott]

An ImportError is raised if Matching.load_from_rustworkx or Matching.to_rustworkx are used without rustworkx installed

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (b802cc5) to head (9e8feba).
Report is 11 commits behind head on master.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff            @@
##            master       #90   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines          338       348   +10     
=========================================
+ Hits           338       348   +10     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.