doc: add missing period

PR-URL: nodejs/node#49094
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>

graal-nodejs/doc/api/policy.md

@@ -6,6 +6,6 @@
 
 > Stability: 1 - Experimental
 
-The former Policies documentation is now at [Permissions documentation][]
+The former Policies documentation is now at [Permissions documentation][].
 
 [Permissions documentation]: permissions.md#policies