net: selftests: Fix optstring

The cited commit added a stray colon to the 'v' option. That makes the
option work incorrectly.

ex:
tools/testing/selftests/net# ./fib_nexthops.sh -v
(should enable verbose mode, instead it shows help text due to missing arg)

Fixes: 5feba472 ("selftests: fib_nexthops: Make ping timeout configurable")
Reviewed-by: NIdo Schimmel <idosch@nvidia.com>
Signed-off-by: NBenjamin Poirier <bpoirier@nvidia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

tools/testing/selftests/net/fib_nexthops.sh

@@ -2283,7 +2283,7 @@ EOF
 ################################################################################
 # main
 
-while getopts :t:pP46hv:w: o
+while getopts :t:pP46hvw: o
 do
 	case $o in
 		t) TESTS=$OPTARG;;