Update error message (#4417)

### What problem does this PR solve?

1. Update error message
2. Remove space characters

### Type of change

- [x] Refactoring

---------

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

rag/utils/infinity_conn.py

@@ -94,7 +94,7 @@ class InfinityConnection(DocStoreConnection):
                 logger.warning(f"{str(e)}. Waiting Infinity {infinity_uri} to be healthy.")
                 time.sleep(5)
         if self.connPool is None:
-            msg = f"Infinity {infinity_uri} didn't become healthy in 120s."
+            msg = f"Infinity {infinity_uri} is unhealthy in 120s."
             logger.error(msg)
             raise Exception(msg)
         logger.info(f"Infinity {infinity_uri} is healthy.")