RFR: 8246037: Shenandoah: update man pages to mention -XX:+UseShenandoahGC [v3]

[Y. Srinivas Ramakrishna]

On Wed, 27 Aug 2025 23:20:37 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Rui Li has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update for comments
>
> src/java.base/share/man/java.md line 2907:
> 
>> 2905:         [JEP 521](https://openjdk.org/jeps/521) for its advantages and risks.
>> 2906: 
>> 2907: `-XX:ShenandoahGCHeuristics=`*heuristics*
> 
> Should probably mention that the generational mode ignores (and now issues a warning) when anything other than `adaptive` is selected.

Good point.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26907#discussion_r2305550427