Clarify pending-invitation billing excludes usage-based GHE

Pending invitations consume licenses under volume/standard seat-based
GitHub Enterprise but not under usage-based (metered) billing. Scope the
statement to enterprises using neither Enterprise Managed Users nor
usage-based billing, and link to the usage-based licenses page.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: lucyji1000

content/billing/reference/github-license-users.md

@@ -51,7 +51,7 @@ category:
   * {% data variables.product.company_short %} counts each outside collaborator once, even if the user account has access to multiple repositories in your organization.
 * Dormant users who are a member or owner of at least one organization in the enterprise
 
-If your enterprise does not use {% data variables.product.prodname_emus %}, you will also be billed for each of the following accounts:
+If your enterprise does not use {% data variables.product.prodname_emus %} or usage-based billing, you will also be billed for each of the following accounts. Under usage-based billing, pending invitations do not consume a license. See [AUTOTITLE](/billing/concepts/enterprise-billing/usage-based-licenses).
 
 * Anyone with a pending invitation to become an organization owner or member
   * If the invited user already consumes an enterprise license, a pending organization invitation won't use an additional license—as long as the invitation is sent to their {% data variables.product.github %} username or a verified email address on their account.