[jdk21u-dev] RFR: 8327289: Remove unused PrintMethodFlushingStatistics option

[Elif Aslan]

Clean backport. This PR removes the option PrintMethodFlushingStatistics. Last usage was removed in [8290025](https://bugs.openjdk.org/browse/JDK-8290025).

GHA tested

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Commit messages:
 - Backport 09b88098ff544fec1a4e94bfbbdc21b6c8433abb

Changes: https://git.openjdk.org/jdk21u-dev/pull/2461/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2461&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327289
  Stats: 3 lines in 1 file changed: 0 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2461.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2461/head:pull/2461

PR: https://git.openjdk.org/jdk21u-dev/pull/2461