RFR: 8307067: remove broken EnableThreadSMRExtraValidityChecks option

[Daniel D. Daugherty]

A trivial fix to remove broken EnableThreadSMRExtraValidityChecks option.

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Commit messages:
 - 8307067: remove broken EnableThreadSMRExtraValidityChecks option

Changes: https://git.openjdk.org/jdk/pull/13704/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13704&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307067
  Stats: 11 lines in 3 files changed: 0 ins; 7 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/13704.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13704/head:pull/13704

PR: https://git.openjdk.org/jdk/pull/13704