Add decorator to translationFragment property

[tobias-kuendig]

Proposed change

I did a fresh checkout of the frontend repo and noticed, the onboarding screen was broken:

This is a tiny change to fix the error message from the screenshot above.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.