Bug 1948550 - test_permmanager_remote.js needs to account for shipped…

… remote settings. r=maltejur

If Thunderbird ships permissions, this test fails since the test doesn't account for that.
Firefox runs the test without Firefox profile settings (meaning no remote settings available) so
it's not a problem there.

Differential Revision: https://phabricator.services.mozilla.com/D239492

extensions/permissions/test/unit/test_permmanager_remote.js

@@ -77,6 +77,10 @@ add_setup(async function () {
 
   await rps.isInitialized;
 
+  // Make sure we start off "empty". Any RemoteSettings values must be
+  // purged now to comply with test expectations.
+  Services.obs.notifyObservers(null, "testonly-reload-permissions-from-disk");
+
   registerCleanupFunction(async () => {
     info("Cleaning up");
     rps.testAllowedPermissionValues = originalPermissionValues;