[DOCS] Fixes typo in realm chains

Author: lcawl

docs/en/stack/security/authentication/realm-chains.asciidoc

@@ -70,7 +70,7 @@ there are
 [[authorization_realms]]
 ==== Delegating authorization to another realm
 
-Some realms have the ability perform _authentication_ internally, but delegate the
+Some realms have the ability to perform _authentication_ internally, but delegate the
 lookup and assignment of roles (that is, _authorization_) to another realm.
 
 For example, you may wish to use a PKI realm to authenticate your users with