fix typo

Author: pwright

modules/rbac-users.adoc

@@ -46,5 +46,5 @@ Service accounts are represented with the `ServiceAccount` object. Examples:
 Each user must authenticate in
 some way to access {product-title}. API requests with no authentication
 or invalid authentication are authenticated as requests by the `anonymous`
-system user. After authenticated, policy determines what the user is
+system user. After authentication, policy determines what the user is
 authorized to do.