[MNT] ci: Bump actions versions

[ales-erjavec]

Issue

From CI logs:

Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: actions/cache@v4, actions/checkout@v4, actions/setup-python@v5, codecov/codecov-action@v4. Actions will be forced to run with Node.js 24 by default starting June 16th, 2026.

Description of changes

• Bump gh actions versions to avoid Node 20 deprecation warnings in CI logs

Includes

• Code changes
• Tests
• Documentation

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.79%. Comparing base (3746fd9) to head (d2283f7).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #296   +/-   ##
=======================================
  Coverage   72.79%   72.79%           
=======================================
  Files          34       34           
  Lines        9240     9240           
=======================================
  Hits         6726     6726           
  Misses       2514     2514           

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