prod_settings_template: Fix confusing {random_token} in comment.

This was a typo in the original implementation; it should say {token}.

zproject/prod_settings_template.py

@@ -85,7 +85,7 @@
 # The noreply address to be used as the sender for certain generated
 # emails.  Messages sent to this address could contain sensitive user
 # data and should not be delivered anywhere.  The default is
-# e.g. noreply-{random_token}@zulip.example.com (if EXTERNAL_HOST is
+# e.g. noreply-{token}@zulip.example.com (if EXTERNAL_HOST is
 # zulip.example.com).  There are potential security issues if you set
 # ADD_TOKENS_TO_NOREPLY_ADDRESS=False to remove the token; see
 # https://zulip.readthedocs.io/en/latest/production/email.html for details.