Update incoming call notification content to "📹 Incoming call"

[bmarty]

Content

Update incoming call notification content to "📹 Incoming call". Do not use the default content anymore.

Motivation and context

Screenshots / GIFs

Before	After

Tests

• Get an incoming call in one of your DM and observe the notification which is displayed. It should have the new text.

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]

The fix is here.

[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

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.22%. Comparing base (c5f3b34) to head (7878f97).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4231   +/-   ##
========================================
  Coverage    80.21%   80.22%           
========================================
  Files         2043     2043           
  Lines        54095    54113   +18     
  Branches      6569     6570    +1     
========================================
+ Hits         43393    43411   +18     
  Misses        8429     8429           
  Partials      2273     2273           

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