Bug 1869880. Enable 'layout.css.page-orientation.enabled' beyond Nightly channels. r=dholbert

Differential Revision: https://phabricator.services.mozilla.com/D196348

modules/libpref/init/StaticPrefList.yaml

@@ -8654,7 +8654,7 @@
 # Enables support for the page-orientation  property inside of CSS @page rules.
 - name: layout.css.page-orientation.enabled
   type: RelaxedAtomicBool
-  value: @IS_NIGHTLY_BUILD@
+  value: true
   mirror: always
   rust: true