Revert "Penalty for undefended rook"

After extensive test Gary says:

"So, after 16k games at 10"+1" on an i7, the undefended rook test
looks to be not good (albeit by a very small margin).
3063 - 3093 - 9844 (-1).

I doubt that is causing the regression, but even so, it looks like
it's not worth keeping, and we can go back to the simpler undefended
minors check."

Signed-off-by: Marco Costalba <mcostalba@gmail.com>