Another audiocontext_test fix

tests/html/audiocontext_test.dart

 library AudioContextTest;
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_individual_config.dart';
 import 'dart:html';
 import 'dart:typed_data';
 import 'dart:web_audio';
 import 'dart:async';
 
 main() {
 
@@ skipping 65 matching lines @@
 
         oscillator.type = 'sine';
         expect(oscillator.type, equals('sine'));
    
         oscillator.type = 'square';
         expect(oscillator.type, equals('square'));
    
         oscillator.type = 'triangle';
         expect(oscillator.type, equals('triangle'));
 
-        expect(() => oscillator.type = 'somethingUnsupported', throws);
-        expect(oscillator.type, equals('triangle'));
-
         expect(() => oscillator.type = 7, throws);
         expect(oscillator.type, equals('triangle'));
 
         expect(() => oscillator.type = ['heap object not a string'], throws);
         expect(oscillator.type, equals('triangle'));
       }
     });
   });
 }