RFR: 8326722: Cleanup unnecessary forward declaration in collectedHeap.hpp

[Zhengyu Gu]

On Tue, 27 Feb 2024 08:33:15 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Trivial cleanup
>
> lgtm and trivial

Thanks, @tschatzl

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PR Comment: https://git.openjdk.org/jdk/pull/18018#issuecomment-1966768910