RFR: 8337982: Remove dead undef assrt0n

[David Holmes]

On Wed, 7 Aug 2024 12:28:55 GMT, Casper Norrbin <duke at openjdk.org> wrote:

> Hello everyone,
> 
> `blockTree.cpp` contains an `#undef` that is never defined anywhere.
> This is dead code should be removed.
> 
> Thanks.

Looks good (and trivial). Seems like a typo introduced by JDK-8256725.

Thanks

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/20493#pullrequestreview-2226884474