[jdk21u] RFR: 8311981: Test gc/stringdedup/TestStringDeduplicationAgeThreshold.java#ZGenerational timed out

[David Holmes]

Hi all,

    This pull request contains a backport of commit [f142470d](https://github.com/openjdk/jdk/commit/f142470deaebbf9cff7f6f28842972393506b7c4) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

    The commit being backported was authored by David Holmes on 14 Aug 2023 and was reviewed by Stefan Karlsson, Patricio Chilano Mateo, Daniel D. Daugherty and Robbin Ehn.

    Thanks!

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Commit messages:
 - Backport f142470deaebbf9cff7f6f28842972393506b7c4

Changes: https://git.openjdk.org/jdk21u/pull/83/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=83&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311981
  Stats: 11 lines in 1 file changed: 9 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk21u/pull/83.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/83/head:pull/83

PR: https://git.openjdk.org/jdk21u/pull/83