The `java.locale.useOldISOCodes` system property has been deprecated. Introduced in JDK 17, it allowed users to revert to the legacy ISO 639 language codes for Hebrew, Indonesian, and Yiddish. Since its purpose was to facilitate a transition to the updated codes, we believe it is now time to retire it. In JDK 25, setting this property to `true` has no effect, and a warning about its future removal is displayed at runtime.