docs: Added message that one should restart the server

fix_entity_names.py

@@ -91,6 +91,7 @@ def main():
         if confirm("Check 'debug.json' if the output looks reasonable then confirm"):
             json.dump(entities_object, entities_file)
             print("Replaced 'core.entity_registry' with the contents of debug.json")
+            print("PLEASE RESTART THE SERVER NOW")
         else:
             print(
                 "Nothing changed. You could try to fix debug.json and replace the original file with it."