Add missing properties in kpackage-generic.desktop

Summary:
Before:
Unknown property type for key "Keywords" -> falling back to string
Unknown property type for key "X-KDE-ParentApp" -> falling back to string

After:
Found property definition "X-KPackage-Dependencies" with type "QStringList"
Found property definition "Keywords" with type "QStringList"

Test Plan: QT_LOGGING_RULES='*=true' kpackagetool5 --appstream-metainfo . --appstream-metainfo-output /tmp/a.xml

Reviewers: mart, apol, sitter

Reviewed By: apol

Subscribers: Frameworks

Differential Revision: https://phabricator.kde.org/D20752