RFR: 8343483: Remove unnecessary @SuppressWarnings annotations (serviceability)

[Archie Cobbs]

@SuppressWarnings annotations that don't actually suppress any warnings create a potential pathway for future bugs to creep in unnoticed. They should be removed if possible.

This issue is for those JDK files with the "serviceability" label.

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Commit messages:
 - Remove unnecessary @SuppressWarnings annotations.

Changes: https://git.openjdk.org/jdk/pull/21857/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21857&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343483
  Stats: 21 lines in 16 files changed: 0 ins; 16 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/21857.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21857/head:pull/21857

PR: https://git.openjdk.org/jdk/pull/21857