Add idle_timeout to reply by email doc.

config/gitlab.yml.example

@@ -138,7 +138,7 @@ production: &base
     # The mailbox where incoming mail will end up. Usually "inbox".
     mailbox: "inbox"
-    # The mailbox where incoming mail will end up. Usually "inbox".
+    # The IDLE command timeout.
     idle_timeout: 60
   ## Build Artifacts

doc/administration/reply_by_email.md

@@ -105,6 +105,8 @@ To set up a basic Postfix mail server with IMAP access on Ubuntu, follow
     # The mailbox where incoming mail will end up. Usually "inbox".
     gitlab_rails['incoming_email_mailbox_name'] = "inbox"
+    # The IDLE command timeout.
+    gitlab_rails['incoming_email_idle_timeout'] = 60
     ```
     ```ruby
@@ -133,6 +135,8 @@ To set up a basic Postfix mail server with IMAP access on Ubuntu, follow
     # The mailbox where incoming mail will end up. Usually "inbox".
     gitlab_rails['incoming_email_mailbox_name'] = "inbox"
+    # The IDLE command timeout.
+    gitlab_rails['incoming_email_idle_timeout'] = 60
     ```
 1. Reconfigure GitLab and restart mailroom for the changes to take effect:
@@ -192,6 +196,8 @@ To set up a basic Postfix mail server with IMAP access on Ubuntu, follow
       # The mailbox where incoming mail will end up. Usually "inbox".
       mailbox: "inbox"
+      # The IDLE command timeout.
+      email_idle_timeout: 60
     ```
     ```yaml
@@ -221,6 +227,8 @@ To set up a basic Postfix mail server with IMAP access on Ubuntu, follow
       # The mailbox where incoming mail will end up. Usually "inbox".
       mailbox: "inbox"
+      # The IDLE command timeout.
+      email_idle_timeout: 60
     ```
 1. Enable `mail_room` in the init script at `/etc/default/gitlab`:
@@ -277,6 +285,8 @@ To set up a basic Postfix mail server with IMAP access on Ubuntu, follow
       # The mailbox where incoming mail will end up. Usually "inbox".
       mailbox: "inbox"
+      # The IDLE command timeout.
+      email_idle_timeout: 60
     ```
     As mentioned, the part after `+` is ignored, and this will end up in the mailbox for `gitlab-incoming@gmail.com`.