If your I/O Board cable's connectors have notches in the padding, you will need to release a locking lever underneath the notch in order to remove the cable. If this is the case, don't pry up on the connector until the levers are unlatched.

Using the flat end of a spudger, pry the I/O Board connector straight up out of its socket on the logic board.

During reassembly, connect this end first, as it does not flex.

In a similar fashion, remove the I/O Board cable connector from its socket on the I/O Board.

Remove the I/O Board cable from the MacBook Pro.