Another cleanup

[bmarty]

Content

Remove useless annotations, seems like some APIs are more stable now.
Also remove dead code about message highlight.

Motivation and context

Clean code

Screenshots / GIFs

Tests

• No expected change in the app behavior.

Tested devices

• Physical
• Emulator
• OS version(s):

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

[bmarty]

Note: there is no diff in the recorded screenshots since this is actually a plain background color like before since isHighlighted had no impact.

[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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.27%. Comparing base (770e16d) to head (9005a51).
Report is 10 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4869      +/-   ##
===========================================
- Coverage    80.28%   80.27%   -0.01%     
===========================================
  Files         2140     2140              
  Lines        56922    56908      -14     
  Branches      7164     7164              
===========================================
- Hits         45698    45685      -13     
  Misses        8789     8789              
+ Partials      2435     2434       -1     

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[jmartinesp]

Thanks!