Re-enable Fulu execution_payload tests

[michaelsproul]

When spec v1.6.0-alpha.1 is released we need to re-enable the tests disabled by this PR:

• Fulu EF tests v1.6.0-alpha.0 #7540

The issue is that we are currently ahead of the spec release v1.6.0-alpha.0, but up to date with dev and devnet-0:

lighthouse/consensus/types/src/chain_spec.rs

Lines 656 to 659 in cd83d8d

	/// Return the value of `MAX_BLOBS_PER_BLOCK` for the given `epoch`.
	/// NOTE: this function is *technically* not spec compliant, but
	/// I'm told this is what the other clients are doing for `devnet-0`..
	pub fn max_blobs_per_block(&self, epoch: Epoch) -> u64 {

We can remove that comment as well when making this change.

The main thing to remove is the skipped known failure:

lighthouse/testing/ef_tests/src/cases/operations.rs

Lines 577 to 586 in d86233d

	// FIXME(das): remove this once v1.6.0-alpha.1 is released
	// We are ahead of the v1.6.0-alpha.0 spec in our implementation of
	// `get_max_blobs_per_block`, so we fail the execution payload test which expects the
	// empty blob schedule to generate an error.
	if O::handler_name() == "execution_payload"
	&& fork_name == ForkName::Fulu
	&& _case_index == 32
	{
	return Err(Error::SkippedKnownFailure);
	}

[jimmygchen]

Completed in #7632