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-simplemouse/game.gd

@@ -140,7 +140,6 @@ func left_click_on_inventory_item(inventory_item_global_id: String, event: Input
 			$mouse_layer/verbs_menu.set_tool_texture(
 				item.inventory_item.texture_normal
 			)
-	
 
 func right_click_on_inventory_item(inventory_item_global_id: String, event: InputEvent) -> void:
 	mousewheel_action(1)