Update cron library for ldap sync (#47983)

* ldap: update cron library

* Update docs/sources/enterprise/enhanced_ldap.md

pkg/extensions/main.go

@@ -1,9 +1,6 @@
 package extensions
 
 import (
-	// Upgrade ldapsync from cron to cron.v3 and
-	// remove the cron (v1) dependency
-
 	_ "cloud.google.com/go/kms/apiv1"
 	_ "github.com/Azure/azure-sdk-for-go/sdk/azidentity"
 	_ "github.com/Azure/azure-sdk-for-go/sdk/keyvault/azkeys"
@@ -24,7 +21,6 @@ import (
 	_ "github.com/linkedin/goavro/v2"
 	_ "github.com/m3db/prometheus_remote_client_golang/promremote"
 	_ "github.com/pkg/errors"
-	_ "github.com/robfig/cron"
 	_ "github.com/robfig/cron/v3"
 	_ "github.com/russellhaering/goxmldsig"
 	_ "github.com/stretchr/testify/require"