fix(_redis): restore Azure-specific kwargs in cluster kwargs set

The set-literal refactor of _get_redis_cluster_kwargs dropped four
LiteLLM-custom Azure keys (azure_redis_ad_token, azure_client_id,
azure_tenant_id, azure_client_secret) that the prior list form had
explicitly appended. Because they are not in RedisCluster's argspec,
they were silently stripped, breaking Azure IAM auth on cluster
clients. Re-add them to the explicit include set.

litellm/_redis.py

@@ -95,6 +95,10 @@ def _get_redis_cluster_kwargs(client=None):
         "redis_connect_func",  # Needed for sync clusters and IAM detection
         "gcp_service_account",
         "gcp_ssl_ca_certs",
+        "azure_redis_ad_token",
+        "azure_client_id",
+        "azure_tenant_id",
+        "azure_client_secret",
         "max_connections",
     }