Bug 1635243. Only use WS_EX_LAYERED | WS_EX_TRANSPARENT on the compositor window on nightly for now. r=sotaro

We haven't shipped direct manipulation yet so we don't need these and they still cause blank windows for a very small number of users.

Differential Revision: https://phabricator.services.mozilla.com/D73749

modules/libpref/init/StaticPrefList.yaml

@@ -568,7 +568,7 @@
 
 - name: apz.windows.force_disable_direct_manipulation
   type: RelaxedAtomicBool
-  value: false
+  value: @IS_NOT_NIGHTLY_BUILD@
   mirror: always
 
 - name: apz.x_skate_highmem_adjust