Align should_extend_payload with Gloas

[jihoonsong]

This PR aligns Heze's `should_extend_payload`` to Gloas.

[jtraglia]

Good catch. And just to confirm, the blank line was deleted in Gloas too.

consensus-specs/specs/gloas/fork-choice.md

Lines 386 to 396 in a6687a2

	def should_extend_payload(store: Store, root: Root) -> bool:
	if not is_payload_verified(store, root):
	return False
	proposer_root = store.proposer_boost_root
	return (
	(is_payload_timely(store, root) and is_payload_data_available(store, root))
	or proposer_root == Root()
	or store.blocks[proposer_root].parent_root != root
	or is_parent_node_full(store, store.blocks[proposer_root])
	)
	```