static/html/pages: update license_policy.tmpl
static/html/pages: update license_policy.tmpl

- Mention that we use licensecheck.
- Ask package users to contact package authors, rather than us.

Change-Id: I4334136d486e2acec128c35c6fc9cc1112fe6c0e
Reviewed-on: https://team-review.git.corp.google.com/c/golang/discovery/+/620961
CI-Result: Cloud Build <ea5729d4cf3392b9d382b6ca272c65aa27554f44@system.gserviceaccount.com>
Reviewed-by: Julie Qiu <e6cb64861edcc38971590ff27c111e0e672de045@google.com>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite