RFR: 8338662: Shenandoah: Remove excessive ShenandoahVerifier::verify_during_evacuation

[William Kemper]

Not clean, combined with a related change.

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Commit messages:
 - Fix merge error
 - 8336915: Shenandoah: Remove unused ShenandoahVerifier::verify_after_evacuation
 - 8338662: Shenandoah: Remove excessive ShenandoahVerifier::verify_during_evacuation

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/129/files
  Webrev: https://webrevs.openjdk.org/?repo=shenandoah-jdk21u&pr=129&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338662
  Stats: 54 lines in 3 files changed: 0 ins; 52 del; 2 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/129.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/129/head:pull/129

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/129