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/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)
-	
-