RFR: 8272461: G1: remove empty declaration of cleanup_after_scan_heap_roots

[Albert Mingkun Yang]

On Fri, 13 Aug 2021 17:12:47 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Trivial change of removing an empty declaration.

Thanks for the review.

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PR: https://git.openjdk.java.net/jdk/pull/5114