Enforce ruff/flake8-return rules (RET)

[DimitriPapadopoulos]

TODO:

• Unit tests and/or doctests in docstrings
• Tests pass locally
• Docstrings and API docs for any new/modified user-facing classes and functions
• Changes documented in docs/release.rst
• Docs build locally
• GitHub Actions CI passes
• Test coverage to 100% (Codecov passes)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.92%. Comparing base (86f5ce4) to head (079d610).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #600      +/-   ##
==========================================
- Coverage   99.92%   99.92%   -0.01%     
==========================================
  Files          62       62              
  Lines        2721     2708      -13     
==========================================
- Hits         2719     2706      -13     
  Misses          2        2              

Files with missing lines	Coverage Δ
numcodecs/astype.py	100.00% <100.00%> (ø)
numcodecs/base64.py	100.00% <100.00%> (ø)
numcodecs/categorize.py	100.00% <100.00%> (ø)
numcodecs/delta.py	100.00% <100.00%> (ø)
numcodecs/fixedscaleoffset.py	100.00% <100.00%> (ø)
numcodecs/gzip.py	100.00% <100.00%> (ø)
numcodecs/quantize.py	100.00% <100.00%> (ø)
numcodecs/tests/test_blosc.py	100.00% <100.00%> (ø)
numcodecs/tests/test_shuffle.py	100.00% <100.00%> (ø)

---- 🚨 Try these New Features:

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