applets/notifications: don't allow horizontal scrolling
Reason for the change
Notification bodies have their width constrained by the notification and the horizontal scrollbar forced off, but they can still be scrolled with a horizontal wheel, touchpad, or similiar. This is surprising and pointless.
Instead explicitly set the contentWidth, which is otherwise ultimately based on the underlying TextEdit (and that's the width it would have on a single line without wrapping).
Test plan
- Get long notification
- Scroll horizontally
Screenshots or screen recordings
Before:
After:
Can't do that anymore
Bugs fixed
N/A