Remove temporary multi touch code

The following methods you added are not used anywhere in the codebase:
- `performTwoPointerGesture`:
https://github.com/selendroid/selendroid/search?q=performTwoPointerGesture

- performMultiPointerGesture, only used by performTwoPointerGesture:
https://github.com/selendroid/selendroid/search?q=performMultiPointerGesture

They were added in https://github.com/selendroid/selendroid/commit/8c873dfdda980b46477d51f2ffaa4f0ee1e471a5

Asked @DominikDary via email and he said it's safe to remove these.