Update webhook retention days for GHES (#56104)

Co-authored-by: Kevin Heis <heiskr@users.noreply.github.com>
Co-authored-by: Vanessa <vgrl@github.com>

Author: 3 people

content/admin/managing-accounts-and-repositories/managing-repositories-in-your-enterprise/troubleshooting-service-hooks.md

@@ -31,7 +31,7 @@ You can find information for the last response of all service hooks deliveries o
 
 ## Viewing past deliveries
 
-Deliveries are stored for 15 days.
+Deliveries are stored for {% data variables.webhooks.retention %} days.
 
 {% data reusables.enterprise_site_admin_settings.access-settings %}
 {% data reusables.enterprise_user_management.service-hooks-sidebar-navigation %}