[PR #9795/fcb790b1 backport][3.11] Switch WebSocketWriter to use removesuffix to drop compression trailer

[patchback]

This is a backport of PR #9795 as merged into master (fcb790b).

Now that Python 3.8 is no longer supported (master and 3.11 only) we can use bytes.removesuffix

This also takes care of one uncovered branch in the tests and brings the WebSocketWriter up to 100% line/branch coverage

Its small improvement, considering how much time the compression actually takes. It will be >10% if using isal for compression though since the compression overhead is far less when using alternative zlib see #9798

[codspeed-hq]

CodSpeed Performance Report

Merging #9805 will not alter performance

_{Comparing patchback/backports/3.11/fcb790b12810cd823a1a138520152dd755f5b2bf/pr-9795 (48588ac) with 3.11 (c6270f2)}

Summary

✅ 16 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.97%. Comparing base (c6270f2) to head (48588ac).
Report is 206 commits behind head on 3.11.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             3.11    #9805   +/-   ##
=======================================
  Coverage   97.97%   97.97%           
=======================================
  Files         119      119           
  Lines       36114    36111    -3     
  Branches     4329     4328    -1     
=======================================
- Hits        35382    35380    -2     
  Misses        546      546           
+ Partials      186      185    -1     

Flag	Coverage Δ
CI-GHA	97.86% <100.00%> (+<0.01%)	⬆️
OS-Linux	97.56% <100.00%> (+<0.01%)	⬆️
OS-Windows	94.39% <100.00%> (+<0.01%)	⬆️
OS-macOS	96.65% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	96.50% <100.00%> (+<0.01%)	⬆️
Py-3.10.15	97.11% <100.00%> (+<0.01%)	⬆️
Py-3.11.10	97.18% <100.00%> (+0.04%)	⬆️
Py-3.11.9	96.58% <100.00%> (+0.01%)	⬆️
Py-3.12.7	97.63% <100.00%> (+<0.01%)	⬆️
Py-3.13.0	97.61% <100.00%> (+<0.01%)	⬆️
Py-3.9.13	96.43% <100.00%> (+<0.01%)	⬆️
Py-3.9.20	97.02% <100.00%> (+0.01%)	⬆️
Py-pypy7.3.16	96.59% <100.00%> (-0.01%)	⬇️
VM-macos	96.65% <100.00%> (+<0.01%)	⬆️
VM-ubuntu	97.56% <100.00%> (+<0.01%)	⬆️
VM-windows	94.39% <100.00%> (+<0.01%)	⬆️

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