RFR: 8373054: Shenandoah: Remove unnecessary BarrierSetNMethod::arm in shenandoahCodeRoots [v2]

[Aleksey Shipilev]

On Wed, 3 Dec 2025 22:07:15 GMT, Ben Taylor <btaylor at openjdk.org> wrote:

>> The call to arm is redundant, and can be replaced with an assert to ensure the precondition remains true.
>> 
>> The same set of tier1 tests pass before and after this change with a fastdebug and Shenandoah GC.
>
> Ben Taylor has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix misleading comment in previous commit

Marked as reviewed by shade (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/28648#pullrequestreview-3538487931