avformat/matroskaenc: Don't write elements with their default value

This has happened when writing chapters: Both editions as well as
chapters are by default not hidden and given that we don't support
writing hidden chapters at all, we don't need to write said elements at
all. The same goes for ChapterFlagEnabled.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavformat/matroskaenc.c

@@ -1400,7 +1400,6 @@ static int mkv_write_chapters(AVFormatContext *s)
     editionentry = start_ebml_master(dyn_cp, MATROSKA_ID_EDITIONENTRY, 0);
     if (mkv->mode != MODE_WEBM) {
         put_ebml_uint(dyn_cp, MATROSKA_ID_EDITIONFLAGDEFAULT, 1);
-        put_ebml_uint(dyn_cp, MATROSKA_ID_EDITIONFLAGHIDDEN , 0);
     }
     for (i = 0; i < s->nb_chapters; i++) {
         ebml_master chapteratom, chapterdisplay;
@@ -1420,10 +1419,6 @@ static int mkv_write_chapters(AVFormatContext *s)
                       (uint32_t)c->id + (uint64_t)mkv->chapter_id_offset);
         put_ebml_uint(dyn_cp, MATROSKA_ID_CHAPTERTIMESTART, chapterstart);
         put_ebml_uint(dyn_cp, MATROSKA_ID_CHAPTERTIMEEND, chapterend);
-        if (mkv->mode != MODE_WEBM) {
-            put_ebml_uint(dyn_cp, MATROSKA_ID_CHAPTERFLAGHIDDEN , 0);
-            put_ebml_uint(dyn_cp, MATROSKA_ID_CHAPTERFLAGENABLED, 1);
-        }
         if ((t = av_dict_get(c->metadata, "title", NULL, 0))) {
             chapterdisplay = start_ebml_master(dyn_cp, MATROSKA_ID_CHAPTERDISPLAY, 0);
             put_ebml_string(dyn_cp, MATROSKA_ID_CHAPSTRING, t->value);