RFR: 8370807: G1: Fix comment about not selecting pinned regions into collection set

[Thomas Schatzl]

Hi all,

  please review this cleanup of the region attribute registration methods.

Testing: gha

Thanks,
  Thomas

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Commit messages:
 - 8370807

Changes: https://git.openjdk.org/jdk/pull/28038/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28038&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370807
  Stats: 32 lines in 6 files changed: 9 ins; 6 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/28038.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28038/head:pull/28038

PR: https://git.openjdk.org/jdk/pull/28038