RFR: 8317534: GenShen: Remove unused code

[William Kemper]

Remove unused code, fix typos, remove empty statements

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Commit messages:
 - remove unused variable
 - Remove unused code

Changes: https://git.openjdk.org/shenandoah/pull/335/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=335&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317534
  Stats: 286 lines in 27 files changed: 0 ins; 267 del; 19 mod
  Patch: https://git.openjdk.org/shenandoah/pull/335.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/335/head:pull/335

PR: https://git.openjdk.org/shenandoah/pull/335