makes KFileMetaData optional again
Summary:
KFileMetaData is not a required dependency to allow build for Android where it is not needed to get data for music files
fix Windows KDE CI build by removing include for KFileMetaData headers
from filescanner.h
Reviewers: Elisa, astippich
Reviewed By: astippich
Differential Revision: https://phabricator.kde.org/D20779