Update actions/checkout action to v4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v3 -> v4

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Release Notes

actions/checkout (actions/checkout)

### [`v4`](https://togithub.com/actions/checkout/blob/HEAD/CHANGELOG.md#v400) [Compare Source](https://togithub.com/actions/checkout/compare/v3...v4) - [Support fetching without the --progress option](https://togithub.com/actions/checkout/pull/1067) - [Update to node20](https://togithub.com/actions/checkout/pull/1436)

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Configuration

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[codecov[bot]]

Codecov Report

Merging #76 (5878fc7) into master (726ff12) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #76   +/-   ##
=======================================
  Coverage   91.75%   91.75%           
=======================================
  Files          12       12           
  Lines         376      376           
  Branches       85       85           
=======================================
  Hits          345      345           
  Misses         10       10           
  Partials       21       21           

Flag	Coverage Δ
unittests	91.75% <ø> (ø)

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