content: @-mentions and global times are scaled too much by system text-size setting

[chrisbobbe]

Expected: With the system text size increased, @-mention text and global-time text are scaled appropriately, like surrounding text

Actual: Text in these elements is too large; larger than surrounding text

Discussion on flutter/flutter#126962 about how this could be fixed upstream.

1x text scaling (default)	>1x text scaling

[chrisbobbe]

Tim seems to have noticed this today, after switching to a new device: #mobile-team > mention styling @ 💬