cerbero: Fix packaging on macOS

Now that libnice is built with Meson, the gstreamer plugin built by
it uses a dylib suffix.
10 jobs for macos-packaging in 48 minutes and 22 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Preparation
passed manifest #85860

00:00:36

 
  Build
canceled cerbero deps fedora x86_64 #85957

canceled cerbero deps windows x86 #85956

passed cerbero deps windows x86_64 #85863

00:47:45

failed cerbero deps fedora x86_64 #85955

01:00:00

failed cerbero deps fedora x86_64 #85861

01:00:00

failed cerbero deps windows x86 #85862

01:00:01

 
  Full Builds
skipped build cerbero cross win32 #85865
skipped build cerbero cross win64 #85866
skipped build cerbero fedora x86_64 #85864