docs: keep the discovery entry inside the Operations section

The merge with main placed it after a blank line, outside the list it
belongs to and flush against the new Development heading.

Author: MegaRedHand

docs/SUMMARY.md

@@ -15,8 +15,8 @@
 - [Checkpoint Sync](./checkpoint_sync.md)
 - [Fork Choice Visualization](./fork_choice_visualization.md)
 - [Data Storage](./data_storage.md)
-
 - [Peer discovery](./discovery.md)
+
 # Development
 
 - [Spec Deviations](./spec_deviations.md)