Integrated: 8351077: Shenandoah: Update comments in ShenandoahConcurrentGC::op_reset_after_collect

[William Kemper]

Clean, trivial comment only change.

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Commit messages:
 - Backport 7c173fde4274a798f299876492a2cd833eee9fdd

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/175/files
  Webrev: https://webrevs.openjdk.org/?repo=shenandoah-jdk21u&pr=175&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351077
  Stats: 5 lines in 1 file changed: 0 ins; 2 del; 3 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/175.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/175/head:pull/175

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/175