t7201: drop pointless "exit 0" at end of subshell

This test employs a for-loop inside a subshell and correctly aborts the
loop and fails the test overall (via "exit 1") if any iteration of the
for-loop fails. Otherwise, it exits the subshell with an explicit but
entirely unnecessary "exit 0", presumably to indicate that all
iterations of the loop succeeded. The &&-chain is broken between the
for-loop and the "exit 0". Rather than fixing the &&-chain, just drop
the pointless "exit 0".

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7201-co.sh

@@ -673,7 +673,6 @@ test_expect_success 'custom merge driver with checkout -m' '
 		do
 			grep $t arm || exit 1
 		done
-		exit 0
 	) &&
 
 	mv arm expect &&