security/vuxml: Remove references to non-existent package.

There never was a grafana10 package. Initially there was www/grafana
providing grafana-8.x. Then a www/grafana9 port was added providing
grafana-9.x. The www/grafana port was subsequently obsoleted, and
then revived, now providing grafana-10.x. I believe the idea is that
going forwards, www/grafana will provide the latest stable release
version and there may be numbered ports for older major versions.

PR: 277631