Downgrade wpebackend-fdo

wpebackend-fdo 1.8.2 is causing UI process lockups when process swapping
from one page in accelerated compositing mode to another that also uses
accelerated compositing mode. It is fixed by
https://github.com/Igalia/WPEBackend-fdo/pull/144, but a downgrade is
the safest bet for our stable runtime.
8 jobs for mcatanzaro/wpebackend-fdo-revert in 21 minutes and 23 seconds (queued for 3 seconds)
latest
Status Name Job ID Coverage
  Build
passed build-aarch64 #1229824
aarch64 gnome-build-meta

00:21:23

passed build-i386 #1229823
x86_64 gnome-build-meta

00:06:59

passed build-x86_64 #1229822
x86_64 gnome-build-meta

00:09:56

 
  Deploy
manual iso-installer-x86_64 #1229829
x86_64 gnome-build-meta allowed to fail manual
manual pinebook-pro-image #1229826
aarch64 gnome-build-meta allowed to fail manual
manual raspberrypi-4-image #1229828
aarch64 gnome-build-meta allowed to fail manual
manual rock64-image #1229827
aarch64 gnome-build-meta allowed to fail manual
manual vm-image-x86_64 #1229825
x86_64 gnome-build-meta allowed to fail manual