Pin commit sha on GitHub actions

[bmarty]

Content

Use full Git SHA instead of version, which is safer according to https://docs.github.com/en/actions/security-for-github-actions/security-guides/security-hardening-for-github-actions#using-third-party-actions

Motivation and context

Safer CI

Closes #4652

Screenshots / GIFs

No changes

Tests

NA

Tested devices

NA

Checklist

• Changes have been tested on an Android device or Android emulator with API 24
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/element-hq/element-x-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request title will be used in the release note, it clearly define what will change for the user
• Pull request includes screenshots or videos if containing UI changes
• You've made a self review of your PR

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.01%. Comparing base (847f8fc) to head (d7abb97).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4653   +/-   ##
========================================
  Coverage    80.01%   80.01%           
========================================
  Files         2107     2107           
  Lines        55836    55836           
  Branches      6970     6970           
========================================
  Hits         44676    44676           
  Misses        8763     8763           
  Partials      2397     2397           

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[github-actions]

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud