puppet: Remove typo'd cron job.

54b6a83412 fixed the typo introduced in 49ad188449, but that does
not clean up existing installs which had the file with the wrong name
already.

Remove the file with the typo'd name, so two jobs do not race, and fix
the typo in the comment.

puppet/zulip/manifests/app_frontend_base.pp

@@ -220,4 +220,8 @@ class zulip::app_frontend_base {
     mode   => '0644',
     source => 'puppet:///modules/zulip/cron.d/fetch-tor-exit-nodes',
   }
+  # This was originally added with a typo in the name.
+  file { '/etc/cron.d/fetch-for-exit-nodes':
+    ensure => absent,
+  }
 }