RFR: 8332254: GenShen: Remove obsolete comments and revert unnecessary formatting changes

[William Kemper]

No code changes here.

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Commit messages:
 - Remove out dated comments and needless changes to other comments

Changes: https://git.openjdk.org/shenandoah/pull/433/files
  Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=433&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332254
  Stats: 11 lines in 1 file changed: 1 ins; 5 del; 5 mod
  Patch: https://git.openjdk.org/shenandoah/pull/433.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/433/head:pull/433

PR: https://git.openjdk.org/shenandoah/pull/433