avformat/mov: set AVFMT_SEEK_TO_PTS flag

Ever since 59ad504696, the demuxer expects its seek arg to be PTS
and adjusts internally to search index by DTS.

libavformat/mov.c

@@ -8006,5 +8006,5 @@ AVInputFormat ff_mov_demuxer = {
     .read_packet    = mov_read_packet,
     .read_close     = mov_read_close,
     .read_seek      = mov_read_seek,
-    .flags          = AVFMT_NO_BYTE_SEEK,
+    .flags          = AVFMT_NO_BYTE_SEEK | AVFMT_SEEK_TO_PTS,
 };