RFR: 8338473: GenShen: Cleanup access levels, whitespace, typos and unused code

[Kelvin Nilsen]

On Thu, 15 Aug 2024 21:10:05 GMT, William Kemper <wkemper at openjdk.org> wrote:

> This change cleans up access levels, uses keyword `override` instead of `virtual`. Fixes whitespace and typos. Removes unused code an unnecessary assert.

Marked as reviewed by kdnilsen (Committer).

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PR Review: https://git.openjdk.org/shenandoah/pull/471#pullrequestreview-2241475453