RFR: 8337972: Problem list jdk/internal/util/ReferencedKeyTest.java

[Doug Simon]

Problem list until [JDK-8336926](https://bugs.openjdk.org/browse/JDK-8336926) is fixed to reduce the noise in testing.

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Commit messages:
 - Problem list jdk/internal/util/ReferencedKeyTest.java

Changes: https://git.openjdk.org/jdk/pull/20488/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20488&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8337972
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20488.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20488/head:pull/20488

PR: https://git.openjdk.org/jdk/pull/20488