Not use toLower on DesktopEntryName

From:
https://specifications.freedesktop.org/desktop-entry-spec/desktop-entry-spec-latest.html#file-naming
The DesktopEntryName contains characters from the set [A-Za-z0-9-_],
it's ok and suppose to have uppercase letters.
It's used to exec kcmodule, but all kcmodule already in lowercase, no matter
if executing kcmodule requires lowercase.

The DesktopEntryName filed is used by xdg-desktop-portal-kde, and it should get right name from kservice.
https://invent.kde.org/plasma/xdg-desktop-portal-kde/-/blob/master/src/appchooserdialog.cpp#L297