RFR: 8346921: Remove unused arg in markWord::must_be_preserved

[Albert Mingkun Yang]

Trivial removing unused method arg.

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Commit messages:
 - trivial

Changes: https://git.openjdk.org/jdk/pull/22900/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22900&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346921
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/22900.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22900/head:pull/22900

PR: https://git.openjdk.org/jdk/pull/22900