Electra: Update spec definition for process_epoch (#14768)

* Electra: Review process_epoch

* Update CHANGELOG.md

CHANGELOG.md

@@ -31,6 +31,7 @@ The format is based on Keep a Changelog, and this project adheres to Semantic Ve
 - Limit consolidating by validator's effective balance.
 - Use 16-bit random value for proposer and sync committee selection filter.
 - Re-organize the content of the `*.proto` files (No functional change).
+- Updated Electra spec definition for `process_epoch`.
 
 ### Deprecated
 

beacon-chain/core/electra/transition.go

@@ -40,14 +40,17 @@ var (
 //	    process_justification_and_finalization(state)
 //	    process_inactivity_updates(state)
 //	    process_rewards_and_penalties(state)
-//	    process_registry_updates(state)
-//	    process_slashings(state)
+//	    process_registry_updates(state)  # [Modified in Electra:EIP7251]
+//	    process_slashings(state)  # [Modified in Electra:EIP7251]
 //	    process_eth1_data_reset(state)
-//	    process_pending_deposits(state)  # New in EIP7251
-//	    process_pending_consolidations(state)  # New in EIP7251
-//	    process_effective_balance_updates(state)
+//	    process_pending_deposits(state)  # [New in Electra:EIP7251]
+//	    process_pending_consolidations(state)  # [New in Electra:EIP7251]
+//	    process_effective_balance_updates(state)  # [Modified in Electra:EIP7251]
 //	    process_slashings_reset(state)
 //	    process_randao_mixes_reset(state)
+//	    process_historical_summaries_update(state)
+//	    process_participation_flag_updates(state)
+//	    process_sync_committee_updates(state)
 func ProcessEpoch(ctx context.Context, state state.BeaconState) error {
 	_, span := trace.StartSpan(ctx, "electra.ProcessEpoch")
 	defer span.End()