Remove openglmixers plugin, moved to -base

Merged into the existing opengl plugin in -base.
6 jobs for move-videoaggregator-compositor-glmixers in 63 minutes and 4 seconds
Status Job ID Name Coverage
  Preparation
passed #70102
gst indent

00:00:28

passed #70101
manifest

00:00:32

 
  Build
passed #70103
build fedora x86_64

00:02:28

 
  Test
passed #70104
check fedora

00:16:55

 
  Full Builds
passed #70105
build android arm64 api28

00:02:35

passed #70106
build cerbero fedora x86_64

00:43:07