qemu-iotests: Remove 091 from quick group

For the purpose of allowing running quick group on tmpfs.
Signed-off-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/group

@@ -97,7 +97,7 @@
 088 rw auto quick
 089 rw auto quick
 090 rw auto quick
-091 rw auto quick
+091 rw auto
 092 rw auto quick
 095 rw auto quick
 097 rw auto backing