Enforce Pylint rules

[DimitriPapadopoulos]

• else-if-used / R5501
• consider-using-augmented-assign / R6104

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/user-guide/*.rst
• Changes documented as a new file in changes/
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[DimitriPapadopoulos]

I don't think releases notes are needed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.86%. Comparing base (dc5334e) to head (4f279d9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2869   +/-   ##
=======================================
  Coverage   61.86%   61.86%           
=======================================
  Files          85       85           
  Lines       10111    10111           
=======================================
  Hits         6255     6255           
  Misses       3856     3856           

Files with missing lines	Coverage Δ
src/zarr/core/codec_pipeline.py	70.09% <100.00%> (ø)
src/zarr/core/group.py	70.24% <100.00%> (ø)

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