Update resource-quotas.md

This line is about 6 years old and has been implemented for some time ;)

https://github.com/kubernetes/website/blame/30e536f6100b4c6a0cebe8b0bab7ebb68fee5cf1~1/docs/admin/resourcequota/index.md#L19
https://kubernetes.slack.com/archives/C8WRR2BB9/p1635968976005100

Author: afirth

content/en/docs/concepts/policy/resource-quotas.md

@@ -22,8 +22,7 @@ be consumed by resources in that namespace.
 
 Resource quotas work like this:
 
-- Different teams work in different namespaces.  Currently this is voluntary, but
-  support for making this mandatory via ACLs is planned.
+- Different teams work in different namespaces. This can be enforced with [RBAC](/docs/reference/access-authn-authz/rbac/).
 
 - The administrator creates one ResourceQuota for each namespace.