LibJS: Improve const-correctness of CalendarDateUntil

Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp

@@ -187,7 +187,7 @@ ThrowCompletionOr<PlainDate*> calendar_date_add(VM& vm, Object& calendar, Value
 }
 
 // 12.2.7 CalendarDateUntil ( calendar, one, two, options [ , dateUntil ] ), https://tc39.es/proposal-temporal/#sec-temporal-calendardateuntil
-ThrowCompletionOr<Duration*> calendar_date_until(VM& vm, Object& calendar, Value one, Value two, Object& options, FunctionObject* date_until)
+ThrowCompletionOr<Duration*> calendar_date_until(VM& vm, Object const& calendar, Value one, Value two, Object const& options, FunctionObject const* date_until)
 {
     // 1. Assert: Type(calendar) is Object.
 

Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h

@@ -46,7 +46,7 @@ Calendar* get_iso8601_calendar(VM&);
 ThrowCompletionOr<Vector<String>> calendar_fields(VM&, Object& calendar, Vector<StringView> const& field_names);
 ThrowCompletionOr<Object*> calendar_merge_fields(VM&, Object& calendar, Object& fields, Object& additional_fields);
 ThrowCompletionOr<PlainDate*> calendar_date_add(VM&, Object& calendar, Value date, Duration&, Object* options = nullptr, FunctionObject* date_add = nullptr);
-ThrowCompletionOr<Duration*> calendar_date_until(VM&, Object& calendar, Value one, Value two, Object& options, FunctionObject* date_until = nullptr);
+ThrowCompletionOr<Duration*> calendar_date_until(VM&, Object const& calendar, Value one, Value two, Object const& options, FunctionObject const* date_until = nullptr);
 ThrowCompletionOr<double> calendar_year(VM&, Object& calendar, Object& date_like);
 ThrowCompletionOr<double> calendar_month(VM&, Object& calendar, Object& date_like);
 ThrowCompletionOr<String> calendar_month_code(VM&, Object& calendar, Object& date_like);