message: specs: Fix channel timeout description
  It's now given in L1-blocks, not seconds any more.
  Also fix a broken link.
diff: @@ -479,7 +479,7 @@ transaction must also be signed by a recognized batch submitter account.
  [channel-timeout]: glossary.md#channel-timeout
  -The channel timeout is a duration (in seconds) during which [channel frames][channel-frame may land on L1 within
  +The channel timeout is a duration (in L1 blocks) during which [channel frames][channel-frame] may land on L1 within
  [batcher transactions][batcher-transaction].
  The acceptable time range for the frames of a [channel][channel] is `[channel_id.timestamp, channel_id.timestamp +
  