RFR: 8323738: Serial: Remove unreachable methods in Generation

[Stefan Karlsson]

On Mon, 15 Jan 2024 15:25:25 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Trivial removing effectively dead code.

The changes look good, but I wonder if it wouldn't be better to also make the functions in DefNewGeneration non-virtual?

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Marked as reviewed by stefank (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17429#pullrequestreview-1821921444