Use misc status code string when a Cast status code description is not available

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=192609475

extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastUtils.java

@@ -89,7 +89,7 @@ import com.google.android.gms.cast.MediaTrack;
       case CastStatusCodes.UNKNOWN_ERROR:
         return "An unknown, unexpected error has occurred.";
       default:
-        return "Unknown: " + statusCode;
+        return CastStatusCodes.getStatusCodeString(statusCode);
     }
   }