RFR: 8319778: Remove unreachable code in ObjectSynchronizer::exit

Fri Nov 10 12:12:11 UTC 2023

In `ObjectSynchronizer::exit` when unlocking on an inflated monitor with `LM_LIGHTWEIGHT` there is a check if the owner is anonymous. That branch should never be take and would indicate that something is wrong with either `ObjectSynchronizer::inflate` or that `ObjectSynchronizer::exit` is trying to unlock a monitor not owned by the `current` thread.

Changes this to an assert instead. Did not condition the assert on `LM_LIGHTWEIGHT` as this property should hold regardless of locking mode.

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Commit messages:
 - 8319778: Remove unreachable code in ObjectSynchronizer::exit

Changes: https://git.openjdk.org/jdk/pull/16602/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16602&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/jdk/pull/16602.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16602/head:pull/16602

PR: https://git.openjdk.org/jdk/pull/16602