RFR: 8331175: Parallel: Remove VerifyRememberedSets

[Albert Mingkun Yang]

Simple removing a gc verification flag. The resulting structure is consistent with the one in Serial.

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Commit messages:
 - pgc-remove-verify

Changes: https://git.openjdk.org/jdk/pull/18968/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18968&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331175
  Stats: 17 lines in 4 files changed: 3 ins; 14 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18968.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18968/head:pull/18968

PR: https://git.openjdk.org/jdk/pull/18968