RFR: 8362532: Test gc/g1/plab/* duplicate command-line options

[Lei Zhu]

Just removed duplicate flag, no other changes.

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Commit messages:
 - 8362532: Test gc/g1/plab/* duplicate command-line options

Changes: https://git.openjdk.org/jdk/pull/26402/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26402&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8362532
  Stats: 9 lines in 2 files changed: 0 ins; 3 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/26402.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26402/head:pull/26402

PR: https://git.openjdk.org/jdk/pull/26402