Increase OggExtractor's confidence

for some ogg content, the mp3 extractor would slide along looking for a
resynchronization point. and find one. Then it reported the same
confidence as the oggextractor. Bump the confidence returned by the
oggextractor so that it won't lose such a tie.

Bug: 137525449
Test: POC in bug
diff --git a/media/extractors/ogg/OggExtractor.cpp b/media/extractors/ogg/OggExtractor.cpp
index 298dab1..4012ece 100644
--- a/media/extractors/ogg/OggExtractor.cpp
+++ b/media/extractors/ogg/OggExtractor.cpp
@@ -1391,7 +1391,7 @@
         return NULL;
     }
 
-    *confidence = 0.2f;
+    *confidence = 0.5f;
 
     return CreateExtractor;
 }