Fix navigation issue when entering recovery key after navigating from the banner

[bmarty]

Content

Motivation and context

Closes #3278

Screenshots / GIFs

Before

EnterRecoveryKeyStuck.mp4

After

EnterRecoveryKeyFixed.mp4

Tests

• Login to an account, but skip the verification step
• Click on the banner to enter the recovery key
• Enter the recovery key

Previous behavior: screen is stuck with a disabled "Continue" button. Need to close the screen manually
Now: navigating back to the room list, the banner is gone

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

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.07%. Comparing base (6b9eb99) to head (646b92a).
Report is 16 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3961   +/-   ##
========================================
  Coverage    83.07%   83.07%           
========================================
  Files         1791     1791           
  Lines        45335    45335           
  Branches      5348     5348           
========================================
  Hits         37661    37661           
  Misses        5799     5799           
  Partials      1875     1875           

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[spaetz]

Fixes #3039
Fixes #3278
I guess.

[ganfra]

I'd prefer we check the state of the backstack here?

                        if(backstack.canPop()){
                            backstack.pop()
                        } else {
                            callbacks.forEach { it.onDone() }
                        }
                    }

[bmarty]

Yes, this is probably safer: 646b92a

[ganfra]

See my remark, but both ways are ok, do as you prefer :)

[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 SonarQube Cloud