Fix add by QR code layout (#5424)

[pt2121]

Type of change

• Feature
• Bugfix
• Technical
• Other :

Content

When showUserCodeCardNameText is gone, showUserCodeCardUserIdText top constraint is missing. Updated the top margin when the referenced view is gone.
54dp is from adding up both views margin tops (50dp + 4dp).

Motivation and context

Addressing #5424

Screenshots / GIFs

Tests

I tested this from the old UI flow and followed the steps in #5424

1. Enable the old flow
2. Open the hamburger menu on the top left
3. Tap the QR code icon

Tested devices

• Physical
• Emulator
• OS version(s): Android 12 and also API 21

Checklist

• Changes has been tested on an Android device or Android emulator with API 21
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request includes a new file under ./changelog.d. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#changelog
• 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
• If you have modified the screen flow, or added new screens to the application, you have updated the test UiAllScreensSanityTest.allScreensTest()

[bmarty]

Perfect, thanks!