How can I remove a switch and terminate a circuit in its place?
Turn off the power at the panel for this circuit (flip the circuit
breaker).
Remove the cover plate from the switch.
Test with a non-contact tester to make sure that there is no power
    in the circuit box.

Unscrew the switch.
Remove the two wires from the switch (unscrew or, if they are press
in types, cut them close to the switch)
Straighten the wires and screw a wire nut over the bare end of each
wire.

Wrap electrical tape over the nuts and the wires.
Carefully bend them back into the box.
Put a blank cover over the box.