settings: Make label for warning when DMing a guest more succinct.

Also explain what the setting does in the help center.

Author: alya

help/guest-users.md

@@ -42,15 +42,19 @@ pricing](/help/zulip-cloud-billing#temporary-users-and-guests) for guest users.
 
 {end_tabs}
 
-## Configure warning for direct messages to guest users
+## Configure warning when composing a DM to a guest
+
+Zulip can display a warning to let users know when recipients for a direct
+message they are composing are guests in your organization. The warning will be
+shown as a banner in the compose box on the web and desktop apps.
 
 {start_tabs}
 
 {tab|desktop-web}
 
 {settings_tab|organization-permissions}
 
-1. Under **Guests**, toggle **Display a warning when composing a direct message with guest user recipients**.
+1. Under **Guests**, toggle **Warn when composing a DM to a guest**.
 
 {!save-changes.md!}
 

web/src/admin.ts

@@ -74,8 +74,7 @@ const admin_settings_label = {
         defaultMessage: "Display “(guest)” after names of guest users",
     }),
     realm_enable_guest_user_dm_warning: $t({
-        defaultMessage:
-            "Display a warning when composing a direct message with guest user recipients",
+        defaultMessage: "Warn when composing a DM to a guest",
     }),
 };