LibJS: Remove GlobalObject from VM::throw_completion()

This is a continuation of the previous five commits.

A first big step into the direction of no longer having to pass a realm
(or currently, a global object) trough layers upon layers of AOs!
Unlike the create() APIs we can safely assume that this is only ever
called when a running execution context and therefore current realm
exists. If not, you can always manually allocate the Error and put it in
a Completion :^)

In the spec, throw exceptions implicitly use the current realm's
intrinsics as well: https://tc39.es/ecma262/#sec-throw-an-exception

Userland/Libraries/LibJS/Runtime/Intl/Intl.cpp

@@ -151,7 +151,7 @@ JS_DEFINE_NATIVE_FUNCTION(Intl::supported_values_of)
     // 8. Else,
     else {
         // a. Throw a RangeError exception.
-        return vm.throw_completion<RangeError>(global_object, ErrorType::IntlInvalidKey, key);
+        return vm.throw_completion<RangeError>(ErrorType::IntlInvalidKey, key);
     }
 
     // 9. Return CreateArrayFromList( list ).