Bug 1727449 - Restore standard AVIF compliance strictness. r=tnikkel

Now that all known issues requiring permissive parsing are addressed, reinstate
standard strictness to maximize the likelihood of surfacing any new issues as
early as possible in 93.

Backed out changeset 70a4376d352a

Differential Revision: https://phabricator.services.mozilla.com/D124214

modules/libpref/init/StaticPrefList.yaml

@@ -5722,7 +5722,7 @@
 # 2 = Strict: reject violations of "should" specification directives
 - name: image.avif.compliance_strictness
   type: RelaxedAtomicInt32
-  value: 0
+  value: 1
   mirror: always
 
 # Whether we apply container-level transforms like mirroring and rotation