RFR: 8342119: Shenandoah: Remove extra ShenandoahUpdateRefsClosure

[Kelvin Nilsen]

On Tue, 15 Oct 2024 08:53:00 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> We have a duplicate `ShenandoahUpdateRefsClosure`, which we use in a few places. For bulk GC operations, we have `ShenandoahConcUpdateRefsClosure` and `ShenandoahSTWUpdateRefsClosure` that are semantically similar to that one. We can drop the `ShenandoahUpdateRefsClosure` in favor of these two existing ones. 
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `hotspot_gc_shenandoah`
>  - [ ] Performance tests (no regressions)

Marked as reviewed by kdnilsen (Author).

-------------

PR Review: https://git.openjdk.org/jdk/pull/21517#pullrequestreview-2373084021