[lilliput-jdk21u:lilliput] RFR: 8319778: Remove unreachable code in ObjectSynchronizer::exit

[Roman Kennke]

Hi all,

This pull request contains a backport of commit [91279fcf](https://github.com/openjdk/jdk/commit/91279fcf058a6bb16a7749c328179ab94227bb8d) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by Axel Boldt-Christmas on 27 Nov 2023 and was reviewed by Roman Kennke, David Holmes, Patricio Chilano Mateo and Daniel D. Daugherty.

Thanks!

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Commit messages:
 - Backport 91279fcf058a6bb16a7749c328179ab94227bb8d

Changes: https://git.openjdk.org/lilliput-jdk21u/pull/20/files
  Webrev: https://webrevs.openjdk.org/?repo=lilliput-jdk21u&pr=20&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319778
  Stats: 23 lines in 3 files changed: 0 ins; 22 del; 1 mod
  Patch: https://git.openjdk.org/lilliput-jdk21u/pull/20.diff
  Fetch: git fetch https://git.openjdk.org/lilliput-jdk21u.git pull/20/head:pull/20

PR: https://git.openjdk.org/lilliput-jdk21u/pull/20