Summary
-------

Clarify the description of `java.locale.useOldISOCodes` system property so that users won't be misguided about the behavior.

Problem
-------

The system property is only read at the runtime startup time, so it is expected that `System.setProperty()` has no effect on the behavior, users would expect that the behavior would be changed based on the `setProperty()` value.

Solution
--------

Add some text, somewhere along the line with the system property is only read at the runtime startup.

Specification
-------------

Replace the paragraph that describes the `java.locale.useOldISOCodes` system property in the class description of `java.util.Locale`

from:

     * <p>For the backward compatible behavior, the system property
     * {@systemProperty java.locale.useOldISOCodes} reverts the behavior
     * back to prior to Java SE 17 one. If the system property is set
     * to {@code true}, those three current language codes are mapped to their
     * backward compatible forms.

to:

     * <p>For the backward compatible behavior, the system property
     * {@systemProperty java.locale.useOldISOCodes} reverts the behavior
     * back to that of before Java SE 17. If the system property is set to
     * {@code true}, those three current language codes are mapped to their
     * backward compatible forms. The property is only read at Java runtime
     * startup and subsequent calls to {@code System.setProperty()} will
     * have no effect.