Sync Package: use Full_Sync_Immediately by default

The new full sync pattern introduced in #13963 should now be the default way to perform a full sync. We will still support the original full sync by allow sites to use a filter.

packages/sync/src/class-modules.php

@@ -40,7 +40,7 @@ class Modules {
 		'Automattic\\Jetpack\\Sync\\Modules\\Meta',
 		'Automattic\\Jetpack\\Sync\\Modules\\Plugins',
 		'Automattic\\Jetpack\\Sync\\Modules\\Stats',
-		'Automattic\\Jetpack\\Sync\\Modules\\Full_Sync',
+		'Automattic\\Jetpack\\Sync\\Modules\\Full_Sync_Immediately',
 		'Automattic\\Jetpack\\Sync\\Modules\\Term_Relationships',
 	);