Remove superfluous exit 0 added in r321702

atf_skip triggers equivalent functionality, which means the `exit 0`
is unreachable code.

PR:		220164
MFC after:	1 month
MFC with:	r321702

tests/sys/geom/class/gate/ggate_test.sh

@@ -209,7 +209,6 @@ load_ggate()
 	if ! kldstat -q -m g_${class}; then
 		if ! geom ${class} load; then
 			atf_skip "could not load module for geom class=${class}"
-			exit 0
 		fi
 	fi
 }