panel-loader: Remove OnlyShowIn check

GNOME Settings does not run outside GNOME anymore, so checking
this property of the .desktop files here is useless.

The desktop files must continue having the OnlyShowIn key, since
we don't want them to show on search of other desktop environments.
11 jobs from gbsneto/early-exit in 2 minutes and 39 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Build
passed #137123
build

00:01:48

 
  Test
passed #137125
asan

00:00:49

passed #137124
test

00:00:39

 
  Manual
manual #137130
allowed to fail manual
armv8
manual #137126
allowed to fail manual
flatpak
manual #137129
allowed to fail manual
msan
manual #137131
allowed to fail manual
ppc64le
manual #137127
allowed to fail manual
tsan
manual #137128
allowed to fail manual
ubsan
 
  Review
manual #137132
allowed to fail manual
review
manual #137133
allowed to fail manual
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