Revert "Prevent kglobalaccel5 getting activated on non-Plasma systems"

This reverts commit 48c33769.

This change broke users of KGlobalAccel run outside of the Plasma
Desktop. This sort of behavior change probably needs to be made during
a major transition like KF6 so that developers have some notice and it
doesn't randomly change and break stuff unexpectedly.

CCBUG: 435420
BUG: 437034
FIXED-IN: 5.83