Bug 1703524 - Disable Software WebRender for popups on nightly. r=gfx-reviewers,jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D111094

modules/libpref/init/StaticPrefList.yaml

@@ -5028,7 +5028,7 @@
 # software backend
 - name: gfx.webrender.software.unaccelerated-widget.allow
   type: RelaxedAtomicBool
-  value: @IS_NIGHTLY_BUILD@
+  value: false
   mirror: always
 
 # Whether to force widgets that don't support acceleration to use WebRender