oggopus: Refer to 'TOC sequence' instead of byte.

This avoids confusion with the number of frames being defined
by more than the first byte with code 3 packets.

Patch from mark4o.

doc/draft-ietf-codec-oggopus.xml

@@ -187,8 +187,8 @@ A decoder SHOULD treat any Opus packet whose duration is different from that of
 <t>
 The coding mode (SILK, Hybrid, or CELT), audio bandwidth, channel count,
  duration (frame size), and number of frames per packet, are indicated in the
- TOC (table of contents) in the first byte of each Opus packet, as described
- in Section&nbsp;3.1 of&nbsp;<xref target="RFC6716"/>.
+ TOC (table of contents) sequence at the beginning of each Opus packet, as
+ described in Section&nbsp;3.1 of&nbsp;<xref target="RFC6716"/>.
 The combination of mode, audio bandwidth, and frame size is referred to as
  the configuration of an Opus packet.
 </t>