RFR: 8355522: Remove the `java.locale.useOldISOCodes` system property [v6]

[Justin Lu]

On Mon, 8 Dec 2025 20:54:34 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>> This PR removes the system property deprecated in JDK 25. If the property is specified at runtime, a warning will be emitted at startup to inform the user that the value is ignored. A corresponding CSR has been drafted as well
>
> Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Apply suggestions from code review
>   
>   Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>

Marked as reviewed by jlu (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/26419#pullrequestreview-3554248730