ci: update codecov/codecov-action in GitHub Actions workflow to v4

[striezel]

Description

This PR updates codecov/codecov-action to v4, it's current version.

References

• It get's rid of the warning in CI due to outdated Node versions used by the older versions of the actions, e.g. as seen here: https://github.com/boostorg/gil/actions/runs/10054788474

  The following actions uses node12 which is deprecated and will be forced to run on node16: codecov/codecov-action@v1.2.1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

  Version 4 of the action uses Node 20.

• As far as I understand, version 1.x of the action has been deprecated: https://about.codecov.io/blog/codecov-uploader-deprecation-plan/

Tasklist

• Ensure all CI builds pass
• Review and approve

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.12%. Comparing base (322c4e2) to head (1f88d18).
Report is 8 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #755   +/-   ##
========================================
  Coverage    82.12%   82.12%           
========================================
  Files          117      117           
  Lines         5355     5355           
========================================
  Hits          4398     4398           
  Misses         957      957           

[mloskot]

Thanks!