RFR: 8294521: Parallel: Remove unused field in UpdateDensePrefixAndCompactionTask

[Albert Mingkun Yang]

On Wed, 28 Sep 2022 12:15:50 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Trivial change of removing dead code.
> 
> Test: build

Thanks for the review.

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PR: https://git.openjdk.org/jdk/pull/10466