Update v2.9 release notes

docs/release-notes/index.md

@@ -1 +1 @@
-version-2.8.md
+version-2.9.md

docs/release-notes/version-2.9.md

@@ -14,6 +14,7 @@ NetBox v2.9 replaces Django's built-in permissions framework with one that suppo
 
 ### Configuration Changes
 
+* If in use, LDAP authentication must be enabled by setting `REMOTE_AUTH_BACKEND` to `'netbox.authentication.LDAPBackend'`. (LDAP configuration parameters in `ldap_config.py` remain unchanged.)
 * `REMOTE_AUTH_DEFAULT_PERMISSIONS` now takes a dictionary rather than a list. This is a mapping of permission names to a dictionary of constraining attributes, or `None`. For example, `['dcim.add_site', 'dcim.change_site']` would become `{'dcim.add_site': None, 'dcim.change_site': None}`.
 
 ### Other Changes