RFR: 8303081: Serial: Remove unused VM_MarkSweep

[Albert Mingkun Yang]

On Wed, 22 Feb 2023 16:01:30 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Trivial removing dead code.

Thanks for the review.

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PR: https://git.openjdk.org/jdk/pull/12720