{lyn7307} disable saving procedural prefabs in the Editor (#4877)

disable saving procedural prefabs in the Editor since the templates are backed by asset files that will change outside the Editor


Signed-off-by: jackalbe <23512001+jackalbe@users.noreply.github.com>

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabSystemComponent.cpp

@@ -815,7 +815,8 @@ namespace AzToolsFramework
 
             if (templateRef.has_value())
             {
-                return templateRef->get().IsDirty();
+                return !templateRef->get().IsProcedural() && // all procedural prefabs are read-only
+                        templateRef->get().IsDirty();
             }
 
             return false;