Fix issue around closure and beartype causing memory leaks

[benoit74]

One more fix for #322

Fix reference cycle in RxRewriter.rewrite caused by beartype_this_package() re-decorating a per-call closure, permanently pinning rewriter objects in memory

I've opened an issue in beartype repo as well: beartype/beartype#673

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.96%. Comparing base (c23b959) to head (e784d56).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #324   +/-   ##
=======================================
  Coverage   99.96%   99.96%           
=======================================
  Files          41       41           
  Lines        2558     2559    +1     
  Branches      364      364           
=======================================
+ Hits         2557     2558    +1     
  Misses          1        1           

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