Set execution_payment field when constructing bid (#4804)

Author: faheelsattar

specs/gloas/builder.md

@@ -119,7 +119,10 @@ to include. They produce a `SignedExecutionPayloadBid` as follows.
 10. Set `bid.value` to be the value (in gwei) that the builder will pay the
     proposer if the bid is accepted. The builder **MUST** have enough excess
     balance to fulfill this bid and all pending payments.
-11. Set `bid.blob_kzg_commitments_root` to be the `hash_tree_root` of the
+11. Set `bid.execution_payment` to zero. A non-zero value indicates a trusted
+    execution-layer payment. Bids with non-zero `execution_payment` **MUST NOT**
+    be broadcast to the `execution_payload_bid` gossip topic.
+12. Set `bid.blob_kzg_commitments_root` to be the `hash_tree_root` of the
     `blobsbundle.commitments` field returned by `engine_getPayloadV5`.
 
 After building the `bid`, the builder obtains a `signature` of the bid by using: