applets/systemtray: don't sort again after calling `setSortLocaleAware`

Reason for the change

setSortLocaleAware already sorts the model.

See https://invent.kde.org/qt/qt/qtbase/-/blob/ba42c48dd460110d02b078c1460be0e268624faa/src/corelib/itemmodels/qsortfilterproxymodel.cpp#L2762

Test plan

Check if tray icons are sorted local aware.

Screenshots or screen recordings

Bugs fixed