Rename config var according to upstream

home-assistant/core#102203 (comment)
home-assistant/core@d6f3cf4

source/_integrations/intent_script.markdown

@@ -44,7 +44,7 @@ intent:
       required: false
       default: false
       type: boolean
-    script_mode:
+    mode:
       description: The [script mode](https://www.home-assistant.io/integrations/script/#script-modes) in which to run the intent script. Use this to define if the intent should be able to run multiple times in parallel.
       required: false
       default: single