RFR: 8367410: ZGC: Remove unused ZNmethodTable::wait_until_iteration_done()

[Thomas Schatzl]

Hi all,

  please review this trivial removal of `ZNmethodTable::wait_until_iteration_done()` as it is never used.

Testing: local compilation

Thanks,
  Thomas

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Commit messages:
 - 8367410

Changes: https://git.openjdk.org/jdk/pull/27223/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27223&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367410
  Stats: 11 lines in 2 files changed: 0 ins; 10 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27223.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27223/head:pull/27223

PR: https://git.openjdk.org/jdk/pull/27223