docs(paperless-ngx): the policy header said TWO and listed three

Pre-existing, and corrected here rather than left because the third item is the
mail rule this PR rewrites. values.yaml already said THREE.

Part of #136

paperless-ngx/templates/paperless-server.networkpolicy.yaml

@@ -7,8 +7,9 @@ which in this repository are two other charts whose Services listen on port 80.
 That last rule is derived from the switch rather than always rendered, so a
 release without Tika does not carry a rule that permits nothing.
 
-TWO THINGS THIS POLICY DOES NOT COVER, and both are real rather than
+THREE THINGS THIS POLICY DOES NOT COVER, and all three are real rather than
-theoretical:
+theoretical (values.yaml lists the same three; this said "TWO" while listing
+three, which is corrected here because the third one is the mail rule below):
 
 1. THE VALKEY SUBCHART'S POD. This chart declares valkey as an optional
    dependency, and the subchart renders its own StatefulSet with its own