Remove flaky test for now.

Remove the 'fping -X 2 --generate 8.8.0.0/29' test, because it
is currently failing on the MacOS runner. Also, I am not sure that
it is a good idea to ping the IPs 8.8.0.1 and 8.8.0.2 and rely on
them being up.

ci/test-10-option-u-x.pl

@@ -46,11 +46,3 @@
 $cmd->stdout_is_eq("Enough hosts reachable (required: 1, reachable: 1)\n");
 $cmd->stderr_is_eq("");
 }
-
-# fping -X
-{
-my $cmd = Test::Command->new(cmd => "fping -X 2 --generate 8.8.0.0/29");
-$cmd->exit_is_num(1);
-$cmd->stdout_is_eq("Not enough hosts reachable (required: 2, reachable: 0)\n");
-$cmd->stderr_is_eq("");
-}