MNT Resolve deprecation warning in test

[GuySartorelli]

See https://www.php.net/manual/en/migration83.deprecated.php about the deprecation
See https://www.php.net/manual/en/reflectionproperty.setvalue.php for the suggested solution

Not targeting 4.0 because this code doesn't exist on that branch.

Issues

• Lots of "Calling ReflectionProperty::setValue() with a single argument is deprecated" in tests .github#309

[GuySartorelli]

Prefer lowest failure is unrelated

[emteknetnz]

We're missing the setAccessible(true) which should still be required according to this comment

isCliOverride is a private static

Is the linked comment wrong? Or is the unit test just wrong?

[GuySartorelli]

The comment says

Calling this method on a static property that is not public will return a ReflectionException stating the property does not exist

That's not happening, so it must be false.
It's from 10 years ago, things have likely changed since then