Delete dysfunctional fork_revert feature (#8891)

I found myself having to update this code for Gloas, and figured we may as well delete it seeing as it doesn't work.

See:

- https://github.com/sigp/lighthouse/issues/4198


  Delete all `fork_revert` logic and the accompanying test.


Co-Authored-By: Michael Sproul <michael@sigmaprime.io>

beacon_node/beacon_chain/src/lib.rs

@@ -26,7 +26,6 @@ pub mod events;
 pub mod execution_payload;
 pub mod fetch_blobs;
 pub mod fork_choice_signal;
-pub mod fork_revert;
 pub mod graffiti_calculator;
 pub mod historical_blocks;
 pub mod historical_data_columns;