[Sprite Editor Window] Slice button is pushed outside the window when using Slice by Cell Count/Size

Steps to repro:

- Import/create a sprite and set the Sprite Mode to Multiple
- open the Sprite Editor window
- click on Slice to open the Slice window
- change Type to Slice by Cell Size or Slice by Cell Count

Result: The button to perform the Slice action is pushed outside the window
Expected: The button should remain inside the borders of the window