RFR: 8351673: Clean up a case of if (LockingMode == LM_LIGHTWEIGHT) in a legacy-only locking mode function

[Coleen Phillimore]

See title for description.
Tested with tier1-4 with PR https://github.com/openjdk/jdk/pull/23981

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Commit messages:
 - 8351673: Clean up a case of if (LockingMode == LM_LIGHTWEIGHT) in a legacy-only locking mode function

Changes: https://git.openjdk.org/jdk/pull/23990/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23990&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351673
  Stats: 4 lines in 1 file changed: 0 ins; 4 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/23990.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23990/head:pull/23990

PR: https://git.openjdk.org/jdk/pull/23990