RFR: 8343484: Remove unnecessary @SuppressWarnings annotations (nio) [v2]

[Archie Cobbs]

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

Archie Cobbs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Update copyright years.
 - Merge branch 'master' into SuppressWarningsCleanup-nio
 - Merge branch 'master' into SuppressWarningsCleanup-nio
 - Remove unnecessary @SuppressWarnings annotations.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/21858/files
  - new: https://git.openjdk.org/jdk/pull/21858/files/5b5fd5f1..6b79f798

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21858&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21858&range=00-01

  Stats: 3225 lines in 123 files changed: 2078 ins; 749 del; 398 mod
  Patch: https://git.openjdk.org/jdk/pull/21858.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21858/head:pull/21858

PR: https://git.openjdk.org/jdk/pull/21858