Update privacy.html.erb

Minor wording change

lib/views/help/privacy.html.erb

@@ -665,7 +665,7 @@
     the benefit of society. There is a benefit to our users in that we offer an
     easy way to make, track and publish Freedom of Information requests. The
     service also has a benefit to the public as any information released in
-    response to the request is publicly available in a historic archive for
+    response to the request is publicly available in a historical archive for
     anyone to use. There is also a benefit to authorities responding to
     requests, in that the automatic publication of the requests reduces
     duplicate requesting.