Merge pull request #2851 from nish112022/patch-2

Update disk_index.md

Author: AnthonyTsu1984

site/en/reference/disk_index.md

@@ -18,6 +18,7 @@ Currently, a vector field only supports one index type. Milvus automatically del
 ## Prerequisites
 
 To use DiskANN, note that
+
 - DiskANN is disabled by default. If you prefer in-memory index over on-disk index, you are advised to disable this feature for a better performance.
   - To disable it, you can change `queryNode.enableDisk` to `false` in your milvus configuration file.
   - To enable it again, you can set `queryNode.enableDisk` to `true`.