Remove daala plugin

Not so useful now that all effort is focused on AV1 instead.
Was only ever enabled with --enable-experimental anyway.

Fixes #848
6 jobs for remove-daala-plugin in 33 minutes and 31 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Preparation
passed #65318
gst indent

00:00:38

passed #65317
manifest

00:00:31

 
  Build
passed #65319
build fedora x86_64

00:02:58

 
  Test
passed #65320
check fedora

00:15:43

 
  Full Builds
passed #65321
build android arm64 api28

00:02:42

passed #65322
build cerbero fedora x86_64

00:10:55