libweston: Remove functions with no implementation/definition

Seems that these functions: weston_compositor_fade()/weston_compositor_unlock()
lost their implementation a while ago.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
2 jobs for remove-functions in 56 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Container Prep
passed #284583
container_prep

00:00:30

 
  Build
passed #284584
build-native-meson

00:00:26