Features: Check for gstreamer gtk plugin for AV support

Fixes #10551
2 jobs for master in 6 minutes and 39 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
failed #22231
code-quality

00:04:19

 
  Build
passed #22232
linux

00:02:20

 
Name Stage Failure
failed
code-quality Test
gajim/common/app.py:231:18: W0612: Unused variable 'widget' (unused-variable)
gajim/common/app.py:231:26: W0612: Unused variable 'name' (unused-variable)
Uploading artifacts for failed job
Uploading artifacts...
Runtime platform
arch=amd64 os=linux pid=13352 revision=943fc252 version=13.7.0
WARNING: coverage.xml: no matching files
ERROR: No files to upload
Cleaning up file based variables
ERROR: Job failed: exit status 1