QrCode intro screen: add subtitle and fix button wording #3632

[bmarty]

Content

Add subtitle and fix button wording.

Motivation and context

Closes #3632

Screenshots / GIFs

See recorded one

Tests

• Check that screenshot is updated and match the design at https://www.figma.com/design/pDlJZGBsri47FNTXMnEdXB/Compound-Android-Templates?node-id=41-10347&t=sOWqqbMWIr3wJpMn-4

Tested devices

• Physical
• Emulator
• OS version(s):

Checklist

• Changes have been tested on an Android device or Android emulator with API 23
• 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
• Pull request includes a sign off
• You've made a self review of your PR

[github-actions]

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[sonarcloud]

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 SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.71%. Comparing base (47dcdef) to head (bf13341).
Report is 10 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3633   +/-   ##
========================================
  Coverage    82.71%   82.71%           
========================================
  Files         1744     1744           
  Lines        41347    41348    +1     
  Branches      5015     5015           
========================================
+ Hits         34199    34200    +1     
  Misses        5377     5377           
  Partials      1771     1771           

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