[Mouse KCM] Fix writing selected profile value
Summary:
Wrote the default value resulting in no change at all.
BUG: 394787
Test Plan: Manually
Reviewers: Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D13270