RFR: 8270929: Obsolete the FilterSpuriousWakeups flag in JDK 19

[David Holmes]

Please review this small change to obsolete the `FilterSpuriousWakeups` flag that was deprecated in JDK 18.

There are no associated doc changes, nor test changes.

Testing: tier1-5 builds (in progress)

Thanks,
David

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Commit messages:
 - 8270929: Obsolete the FilterSpuriousWakeups flag in JDK 19

Changes: https://git.openjdk.java.net/jdk/pull/6871/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6871&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8270929
  Stats: 9 lines in 3 files changed: 1 ins; 7 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6871.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6871/head:pull/6871

PR: https://git.openjdk.java.net/jdk/pull/6871