Remove 'method' from cmd_move_window_to_position

Remove 'method' from cmd_move_window_to_position

For command:
move window to [absolute] position X px Y px
if the optional keyword 'absolute' is provided the end result is the
same even though it is implemented differently. Only difference is that
with absolute the floating window can move completely outside of any
output.

This commit removes the 'method' argument and only keeps the sane
implementation.