Delete it and refer to your version control system's history if you need to bring it back?

Edited addition to reduce the snarkiness a bit: if I see a block of dead code like that left in a file, regardless of which way it's been killed, I'm going to consider that bad unless there's a very clear comment explaining why this isn't needed anymore but was worth leaving in the code instead of fully deleting it. But if that comment's there, and the reason makes sense, it's still breaking the "rule" but becomes an example of knowing when to break the rule.