Revert "demux_edl: disallow nested edl to avoid infinite loop"

Apparently there are some scripts that use nested edls instead of
flattening them first, so let's live with this.

This reverts commit de42e11662.

DOCS/interface-changes/edl.txt

@@ -1 +0,0 @@
-nested edl are no longer supported; flatten the edl or use a playlist with multiple edl entries

demux/demux_edl.c

@@ -451,10 +451,6 @@ static struct timeline_par *build_timeline(struct timeline *root,
         struct tl_part *part = &parts->parts[n];
         struct demuxer *source = NULL;
 
-        if (!bstrcasecmp0(mp_split_proto(bstr0(part->filename), NULL), "edl")) {
-            MP_ERR(root, "Nested EDL is not allowed.\n");
-            goto error;
-        }
         if (tl->dash) {
             part->offset = starttime;
             if (part->length <= 0)