RFR: 8315973: Remove unused fields from ThreadLocalRandom

[Andrey Turbanov]

These messages were used before [JDK-8248862](https://bugs.openjdk.org/browse/JDK-8248862)

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Commit messages:
 - [PATCH] Remove unused fields from ThreadLocalRandom

Changes: https://git.openjdk.org/jdk/pull/15363/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15363&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315973
  Stats: 9 lines in 1 file changed: 0 ins; 9 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15363.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15363/head:pull/15363

PR: https://git.openjdk.org/jdk/pull/15363