[jdk21u] RFR: 8311823: Remove JFR: Uninitialized EventEmitter::_thread_id field

[Elif Aslan]

[JDK-8311823 ](https://bugs.openjdk.org/browse/JDK-8311823)

Remove Uninitialized EventEmitter::_thread_id field from src/hotspot/share/jfr/leakprofiler/checkpoint/eventEmitter.hpp

GHA tests pass

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Commit messages:
 - Remove JFR: Uninitialized EventEmitter::_thread_id field

Changes: https://git.openjdk.org/jdk21u/pull/191/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=191&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311823
  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u/pull/191.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/191/head:pull/191

PR: https://git.openjdk.org/jdk21u/pull/191