LibJS: Ensure relevant extension keys are included in ICU locale data

This is a normative change in the ECMA-402 spec. See:
7508197

In our implementation, we don't have the affected AOs directly, as we
delegate to ICU. So instead, we must ensure we provide ICU a locale with
the relevant extension keys present.

Libraries/LibUnicode/NumberFormat.h

@@ -142,7 +142,6 @@ class NumberFormat {
 public:
     static NonnullOwnPtr<NumberFormat> create(
         StringView locale,
-        StringView numbering_system,
         DisplayOptions const&,
         RoundingOptions const&);