RFR: 8368752: Serial: Remove unused arg of DefNewGeneration::gc_epilogue

[Francesco Andreuzzi]

On Fri, 26 Sep 2025 08:56:11 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Trivial removing dead code.
> 
> Test: tier1

Marked as reviewed by fandreuzzi (Author).

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PR Review: https://git.openjdk.org/jdk/pull/27516#pullrequestreview-3271260901