Fix elasticsearch status display (#3487)

### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

---------

Signed-off-by: jinhai <haijin.chn@gmail.com>

rag/utils/es_conn.py

@@ -63,7 +63,9 @@ class ESConnection(DocStoreConnection):
         return "elasticsearch"
 
     def health(self) -> dict:
-        return dict(self.es.cluster.health()) + {"type": "elasticsearch"}
+        health_dict = dict(self.es.cluster.health())
+        health_dict["type"] = "elasticsearch"
+        return health_dict
 
     """
     Table operations