RFR: 8274546: Shenandoah: Remove unused ShenandoahUpdateRootsTask copy

[Zhengyu Gu]

On Thu, 30 Sep 2021 09:23:48 GMT, Yude Lin <github.com+16811675+linade at openjdk.org> wrote:

> Remove the unused ShenandoahUpdateRootsTask duplicate from shenandoahConcurrentMark.cpp

Looks good. Thanks for cleaning up.

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Marked as reviewed by zgu (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/5770