Remove useless test for impossible content

What happens in this case is a "do not care" in our truth table for
fitting segments.

test/dash/dash_parser_manifest_unit.js

@@ -287,42 +287,6 @@ describe('DashParser Manifest', () => {
         }));
   });
 
-  it('rejects periods after one without duration', async () => {
-    const periodContents = [
-      '    <AdaptationSet mimeType="video/mp4" lang="en" group="1">',
-      '      <Representation bandwidth="100">',
-      '        <SegmentTemplate startNumber="1" media="l-$Number$.mp4">',
-      '          <SegmentTimeline>',
-      '            <S t="0" d="10" />',
-      '          </SegmentTimeline>',
-      '        </SegmentTemplate>',
-      '      </Representation>',
-      '    </AdaptationSet>',
-    ].join('\n');
-    const template = [
-      '<MPD mediaPresentationDuration="PT75S">',
-      '  <Period id="1">',
-      '%(periodContents)s',
-      '  </Period>',
-      '  <Period id="2">',
-      '%(periodContents)s',
-      '  </Period>',
-      '</MPD>',
-    ].join('\n');
-    const source = sprintf(template, {periodContents: periodContents});
-
-    fakeNetEngine.setResponseText('dummy://foo', source);
-    /** @type {shaka.extern.Manifest} */
-    const manifest = await parser.start('dummy://foo', playerInterface);
-    const video = manifest.variants[0].video;
-    await video.createSegmentIndex();
-
-    // The first period has a segment from 0-10.
-    // With the second period skipping, we should fail to find a segment at 10.
-    expect(video.segmentIndex.find(0)).not.toBe(null);
-    expect(video.segmentIndex.find(10)).toBe(null);
-  });
-
   it('calculates Period times when missing', async () => {
     const periodContents = [
       '    <AdaptationSet mimeType="video/mp4" lang="en" group="1">',