Remove unused method

Author: litetex

app/src/main/java/org/schabi/newpipe/player/helper/PlayerHelper.java

@@ -117,18 +117,6 @@ public static String formatPitch(final double pitch) {
         return PITCH_FORMATTER.format(pitch);
     }
 
-    @NonNull
-    public static String subtitleMimeTypesOf(@NonNull final MediaFormat format) {
-        switch (format) {
-            case VTT:
-                return MimeTypes.TEXT_VTT;
-            case TTML:
-                return MimeTypes.APPLICATION_TTML;
-            default:
-                throw new IllegalArgumentException("Unrecognized mime type: " + format.name());
-        }
-    }
-
     @NonNull
     public static String captionLanguageOf(@NonNull final Context context,
                                            @NonNull final SubtitlesStream subtitles) {