docs: LDAP - added upgrade warning

Signed-off-by: mbshields <[email protected]>

docs/general/whats-new.md

@@ -34,6 +34,8 @@
 
 - The LDAP credentials are removed from zot's LDAP configuration and stored in a separate file. See zot's [LDAP documentation](../articles/authn-authz.md).
 
+    :warning: This LDAP configuration change is incompatible with previous zot releases. When upgrading, you must reconfigure your LDAP credentials if you use LDAP.
+
 ### Storage deduplication on startup
 
 - [Deduplication](../articles/storage.md), a storage space saving feature, now runs or reverts at startup depending on whether the feature is enabled or disabled. You can trigger deduplication by enabling it and then restarting zot.