Remove redundant subscribe_all_data_column_subnets field from network

[jimmygchen]

Issue Addressed

Addresses this comment: #8254 (comment)

We're currently using subscribe_all_data_column_subnets here to subscribe to all subnets

lighthouse/beacon_node/lighthouse_network/src/types/topics.rs

Lines 82 to 92 in 522bd9e

	if fork_name.fulu_enabled() {
	if opts.subscribe_all_data_column_subnets {
	for i in 0..spec.data_column_sidecar_subnet_count {
	topics.push(GossipKind::DataColumnSidecar(i.into()));
	}
	} else {
	for subnet in &opts.sampling_subnets {
	topics.push(GossipKind::DataColumnSidecar(*subnet));
	}
	}
	}

But its unnecessary because the else path also works for supernode (uses sampling_subnets instead)

The big diffs will disappear once #8254 is merged.

[mergify]

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