Remove MP4 Default Quality preset (closes #475)

Similar to High Quality, it is too unpredictable, sometimes giving bad quality
and sometimes being unbearably slow. We should just encourage everyone to set
their bitrate manually.

src/main/java/com/replaymod/render/RenderSettings.java

@@ -62,8 +62,6 @@ public class RenderSettings {
     public enum EncodingPreset {
         MP4_CUSTOM("-an -c:v libx264 -b:v %BITRATE% -pix_fmt yuv420p \"%FILENAME%\"", "mp4"),
 
-        MP4_DEFAULT("-an -c:v libx264 -preset ultrafast -pix_fmt yuv420p \"%FILENAME%\"", "mp4"),
-
         MP4_POTATO("-an -c:v libx264 -preset ultrafast -crf 51 -pix_fmt yuv420p \"%FILENAME%\"", "mp4"),
 
         WEBM_CUSTOM("-an -c:v libvpx -b:v %BITRATE% -pix_fmt yuv420p \"%FILENAME%\"", "webm"),