Sync startplasma with a startkde change

Summary:
bc1324ceebbd71d1571d3adb51371b17391ab425 in startkde had a change

Don't try to set $qdbus to a path to qdbus... it wasn't used
conherently, without issue don't really need it

this wasn't synced with startplasma.

BUG: 374402

Reviewers: Plasma

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D3915