Globe default value

The `$globe` parameter of the constructor always had a default value, right? What I'm doing here is just reimplementing the exact same semantics in a slightly different way, right?

Before: `new GlobeCoordinateValue( $latLang, $precision )` was possible but `new GlobeCoordinateValue( $latLang, $precision, null )` failed. Doesn't make much sense if you think about, especially in terms of deserialization.

After: Both calls use the default value.

[Bug: 66632](https://bugzilla.wikimedia.org/show_bug.cgi?id=66632)