Remove SignInWithClassic FeatureFlag to enable the feature.

[bmarty]

Closes #6669

Draft, as we do not want to merge it now. But it can be reviewed, so we are ready to merge whenever we want.

[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

[ElementBot]

	Warnings
⚠️	features/login/impl/src/main/kotlin/io/element/android/features/login/impl/classic/ElementClassicConnection.kt#L206 - This Handler class should be static or leaks might occur (io.element.android.features.login.impl.classic.DefaultElementClassicConnection.IncomingHandler)

Generated by 🚫 dangerJS against fabdcee

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.35%. Comparing base (8b8eedb) to head (fabdcee).
⚠️ Report is 5 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #6698   +/-   ##
========================================
  Coverage    81.35%   81.35%           
========================================
  Files         2630     2630           
  Lines        73372    73360   -12     
  Branches      9517     9515    -2     
========================================
- Hits         59689    59680    -9     
+ Misses       10180    10178    -2     
+ Partials      3503     3502    -1     

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[bmarty]

Note: we will include this on EXA 26.05.1