refactor: remove trailing whitespace from all .gd files

Not sure why these files were not included in
https://github.com/godot-escoria/escoria-demo-game/pull/494.

Created this diff by running the following on Linux:

```
find -name \*.gd | xargs sed -i -e "s/[[:space:]]\+$//g"
```

addons/escoria-ui-9verbs/game.gd

@@ -275,7 +275,6 @@ func inventory_item_unfocused() -> void:
 		ESCActionManager.ACTION_INPUT_STATE.AWAITING_ITEM:
 			tooltip.set_target("")
 			verbs_menu.unselect_actions()
-	
 		ESCActionManager.ACTION_INPUT_STATE.AWAITING_TARGET_ITEM:
 			tooltip.set_target2("")
 

addons/escoria-ui-9verbs/verbs_menu.gd

@@ -30,5 +30,3 @@ func set_by_name(action_name: String):
 	selected_action = action_name
 	for but in get_children():
 		but.set_pressed(but.get_name() == action_name)
-	
-

addons/escoria-ui-simplemouse/game.gd

@@ -141,7 +141,6 @@ func left_click_on_inventory_item(inventory_item_global_id: String, event: Input
 				item.inventory_item.texture_normal
 			)
 
-
 func right_click_on_inventory_item(inventory_item_global_id: String, event: InputEvent) -> void:
 	mousewheel_action(1)