RFR: 8270171: Shenandoah: Cleanup TestStringDedup and TestStringDedupStress tests

[Aleksey Shipilev]

On Fri, 9 Jul 2021 13:23:56 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> Please review this trivial patch to cleanup TestStringDedup and TestStringDedupStress tests, removes unused Unsafe usages.
> 
> Test:
> - [x] Both tests still pass

Ah yes, `java.lang:open` already provides this. Good!

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Marked as reviewed by shade (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4742