[RTL] Fix character effect offset.

[bruvzg]

Before	After

Note: I have changed the offset effect code in the MRP to make it compatible with wave (add offset to it instead of overriding it):

func _process_custom_fx(char_fx):
	char_fx.offset += Vector2(10, 10)
	return true

Fixes #101496

[akien-mga]

Thanks!