[mediaframe applet] Enable wrapping of fill mode description in config UI

Summary:
Especially with some translations the text will not fit on a single line.

BUG: 393232

Reviewers: #plasma, aspotashev

Reviewed By: aspotashev

Subscribers: aspotashev, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D12307