Use removeprefix and removesuffix string methods

[johannaengland]

These methods have been added to Python 3.9: https://peps.python.org/pep-0616/

They remove the prefix/suffix if it exists and do nothing to the string if not.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.35%. Comparing base (0a90566) to head (a917a22).
Report is 389 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2911      +/-   ##
==========================================
- Coverage   56.35%   56.35%   -0.01%     
==========================================
  Files         603      603              
  Lines       43862    43850      -12     
  Branches       48       48              
==========================================
- Hits        24719    24712       -7     
+ Misses      19131    19126       -5     
  Partials       12       12              

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[github-actions]

Test results

       9 files         9 suites   7m 46s ⏱️
3 320 tests 3 320 ✔️ 0 💤 0 ❌
6 379 runs  6 379 ✔️ 0 💤 0 ❌

Results for commit 93088aa.

[stveit]

From what I can see the logic should be unchanged from this 👍