uplift(release): fix: relative date format crash (#11154)

[wmontwe]

Resolves #11216

The fix works for beta 21.0b1 and is ready to be uplifted to release.

[thunderbird-botmobile]

Thank you for your uplift request! Please add a comment with the following approval request template filled out.

[Approval Request]
Original Issue/Pull request: #11153 / #11154
Regression caused by (issue #): n/a
User impact if declined: Out of memory crash when opening mail boxes with a lot of message
Testing completed (on daily, beta, etc.): daily, beta 21.0b1
Introduces or modifies localizable strings (yes/no): no
Skips a database migration (yes/no): no
Risk to taking this patch (and alternatives if risky): The beta release doesn't show new crashes related to these changes.

[github-actions]

✅ Validation Passed: All report and feature-flag labels are correctly set.