RFR: 8309760: ProblemList serviceability/jvmti/vthread/FollowReferences/VThreadStackRefTest.java#default with ZGC

[Daniel D. Daugherty]

A trivial fix to ProblemList serviceability/jvmti/vthread/FollowReferences/VThreadStackRefTest.java#default with ZGC

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Commit messages:
 - 8309760: ProblemList serviceability/jvmti/vthread/FollowReferences/VThreadStackRefTest.java#default with ZGC

Changes: https://git.openjdk.org/jdk/pull/14406/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14406&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309760
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14406.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14406/head:pull/14406

PR: https://git.openjdk.org/jdk/pull/14406