RFR: 8331004: Serial: Remove unused GenClosure [v2]

[Guoxiong Li]

On Wed, 24 Apr 2024 07:43:44 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Trivial removing dead code.
>
> Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review

Marked as reviewed by gli (Committer).

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PR Review: https://git.openjdk.org/jdk/pull/18922#pullrequestreview-2019284745