Handle Gimp 2.10

Summary:
GIMP 2.10 is still being a bad desktop citizen and requires a workaround
of this sort as well.

A nicer fix to do at a later time would be a regex-based rewriting rule
that won't need version updates.

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D21954