Previously we had 1.6.1 but now there is 1.6.6. However after 1.6.2
libadwaita decided in a minor release to redo their build system to no
longer pre-generate CSS but instead push that on downstreams.
Ignoring the wisdom of doing this in a minor release, just work around
it by manually backporting the changes. They don't affect any CSS which
would need to be regenerated anyway.
Resolves: RHEL-86191
