RFR: 8343477: Remove unnecessary @SuppressWarnings annotations (compiler)

[Archie Cobbs]

Please review this patch which removes unnecessary `@SuppressWarnings` annotations.

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Commit messages:
 - Merge branch 'master' into SuppressWarningsCleanup-compiler
 - Apply change that was missed somehow.
 - Undo change that will be moved to the core-libs branch.
 - Remove unnecessary @SuppressWarnings annotations.

Changes: https://git.openjdk.org/jdk/pull/21851/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21851&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343477
  Stats: 22 lines in 17 files changed: 0 ins; 18 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/21851.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21851/head:pull/21851

PR: https://git.openjdk.org/jdk/pull/21851