Bug 1875257 - Part 3: Remove dom.screenwakelock.testing r=dom-core,edgar

`test_driver.set_permission()` should now just work with the marionette pref.

Differential Revision: https://phabricator.services.mozilla.com/D199211

modules/libpref/init/StaticPrefList.yaml

@@ -3446,12 +3446,6 @@
   value: true
   mirror: always
 
-# Prevent errors when using set_permission from permissions.sys.mjs
-- name: dom.screenwakelock.testing
-  type: bool
-  value: false
-  mirror: always
-
 # Whether to enable the JavaScript start-up cache. This causes one of the first
 # execution to record the bytecode of the JavaScript function used, and save it
 # in the existing cache entry. On the following loads of the same script, the

testing/web-platform/meta/screen-wake-lock/__dir__.ini

@@ -1 +1 @@
-prefs: [marionette.setpermission.enabled:true, dom.screenwakelock.enabled:true, dom.screenwakelock.testing:true]
+prefs: [marionette.setpermission.enabled:true, dom.screenwakelock.enabled:true]