Moving 'screen-capture' sound effect from gsd to gnome-shell

This allows the shell to start the visual flash and auditory click
sound at the same time, between the actual screen capture and the
compression of the PNG.

Reduces perceived latency of the screenshot effect significantly
on very high resolution screens, especially paired with slow CPUs.

Companion shell patch: GNOME/gnome-shell!211
2 jobs for fast-flash in 13 minutes and 52 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Build
passed #95439
build

00:04:38

 
  Test
passed #95440
test

00:09:13