Improve webrtc fuzzer coverage of VP9 bitstream parser.

Bug: webrtc:12354
Change-Id: Ia8e2c7f68eb6c21d386eaf919960cb67a9db9285
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/229027
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34786}

test/fuzzers/vp9_qp_parser_fuzzer.cc

@@ -12,7 +12,6 @@
 
 namespace webrtc {
 void FuzzOneInput(const uint8_t* data, size_t size) {
-  int qp;
-  vp9::GetQp(data, size, &qp);
+  vp9::ParseIntraFrameInfo(data, size);
 }
 }  // namespace webrtc