[jdk21u-dev] RFR: 8321470: ThreadLocal.nextHashCode can be static final

[Satyen Subramaniam]

Backporting JDK-8321470: ThreadLocal.nextHashCode can be static final. Minor change makes the variable final (it is already static). Patch is clean.

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Commit messages:
 - Backport c42535f

Changes: https://git.openjdk.org/jdk21u-dev/pull/1099/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1099&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321470
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1099.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1099/head:pull/1099

PR: https://git.openjdk.org/jdk21u-dev/pull/1099