RFR: 8355650: Remove unused fields in ParkEvent

[Zhengyu Gu]

Please review this trivial change that removes unused `TState` and `Notified` members in `ParkEvent`.

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Commit messages:
 - 8355650: Remove unused fields in ParkEvent

Changes: https://git.openjdk.org/jdk/pull/24902/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24902&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355650
  Stats: 6 lines in 1 file changed: 0 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24902.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24902/head:pull/24902

PR: https://git.openjdk.org/jdk/pull/24902