[MINOR] fix(doc): Fix a JSON format error in doc manage-metadata-usin…

…g-gravitino.md (#1228)

### What changes were proposed in this pull request?

Fix a low-level error in the document `manage-metadata-using-gravitino`

### Why are the changes needed?

Just fix error. 

### Does this PR introduce _any_ user-facing change?

N/A

### How was this patch tested?

N/A

docs/manage-metadata-using-gravitino.md

@@ -916,6 +916,7 @@ curl -X PUT -H "Accept: application/vnd.gravitino.v1+json" \
       "property": "key3",
       "value": "value3"
     }
+  ]  
 }' http://localhost:8090/api/metalakes/metalake/catalogs/catalog/schemas/schema/tables/table
 ```