[YouTube] Fix test for non existent streams

Now YouTube returns just "{}" without any better explanation, so ParsingException is thrown by the extractor. Now users won't get told that the video they are trying to watch does not exist at all, but since YouTube literally provides an empty JSON response we have no way to detect if the video does not exist or if there is some other bug in the way we make requests that causes an empty response.

Author: Stypox

extractor/src/test/java/org/schabi/newpipe/extractor/services/youtube/stream/YoutubeStreamExtractorDefaultTest.java

@@ -86,7 +86,7 @@ void nonExistentFetch() throws Exception {
 
             final StreamExtractor extractor =
                     YouTube.getStreamExtractor(BASE_URL + "don-t-exist");
-            assertThrows(ContentNotAvailableException.class, extractor::fetchPage);
+            assertThrows(ParsingException.class, extractor::fetchPage);
         }
 
         @Test
@@ -280,7 +280,6 @@ protected StreamExtractor createExtractor() throws Exception {
         @Nullable @Override public String expectedTextualUploadDate() { return "2021-03-17T12:56:59-07:00"; }
         @Override public long expectedLikeCountAtLeast() { return 2300; }
         @Override public long expectedDislikeCountAtLeast() { return -1; }
-        @Override public boolean expectedHasSubtitles() { return false; }
         @Override public int expectedStreamSegmentsCount() { return 13; }
         @Override public String expectedLicence() { return YOUTUBE_LICENCE; }
         @Override public String expectedCategory() { return "News & Politics"; }