drop X-DBUS-StartupType key from kcolorchooser.desktop

kcolorchooser doesn't seem to support it, and reports on quit:
KDEInit could not launch
as reported downstream at
https://bugzilla.redhat.com/1337937
https://bugs.mageia.org/show_bug.cgi?id=18307

Runs fine after, no KDEInit errors on close

BUGS: 363051
REVIEW: 127978