RFR: 8344579: Clean up forward declarations

[Coleen Phillimore]

I was looking through the sources for something and found these forward declarations that should be removed. Please review this trivial change.

Sanity tested with tier1.  Will also verify GHA pass.

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Commit messages:
 - 8344579: Clean up forward declarations

Changes: https://git.openjdk.org/jdk/pull/22258/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22258&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344579
  Stats: 8 lines in 4 files changed: 0 ins; 8 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/22258.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22258/head:pull/22258

PR: https://git.openjdk.org/jdk/pull/22258