test: Remove bogus MediaSourceEngine test case (#6465)

MediaSourceEngine does not, in fact, preserve SourceBuffer properties
when we reset it to switch codecs. This is handled by StreamingEngine
instead, through a follow-up call to setStreamProperties.

The test only ever passed as originally written because there was a
missing `await` on an async reset process.

This removes the bogus test.

Related to #6458, #6462

test/media/media_source_engine_unit.js

@@ -1265,30 +1265,6 @@ describe('MediaSourceEngine', () => {
       expect(mockMediaSource.addSourceBuffer).toHaveBeenCalledTimes(2);
     });
 
-    // TODO: Fix this test/feature.  This only passed before because the
-    // original author failed to await the reset. */
-    xit('should persist the previous source buffer parameters', async () => {
-      await mediaSourceEngine.init(initObject, false);
-
-      audioSourceBuffer.timestampOffset = 10;
-      audioSourceBuffer.appendWindowStart = 5;
-      audioSourceBuffer.appendWindowEnd = 20;
-
-      videoSourceBuffer.timestampOffset = 20;
-      videoSourceBuffer.appendWindowStart = 15;
-      videoSourceBuffer.appendWindowEnd = 30;
-
-      await resetMSE(initObject);
-
-      expect(audioSourceBuffer.timestampOffset).toBe(10);
-      expect(audioSourceBuffer.appendWindowStart).toBe(5);
-      expect(audioSourceBuffer.appendWindowEnd).toBe(20);
-
-      expect(videoSourceBuffer.timestampOffset).toBe(20);
-      expect(videoSourceBuffer.appendWindowStart).toBe(15);
-      expect(videoSourceBuffer.appendWindowEnd).toBe(30);
-    });
-
     it('should preserve autoplay and paused state', async () => {
       await mediaSourceEngine.init(initObject, false);