message: [docs] add release note for change to GBT
  GBT must now be called with the segwit rule.
diff: @@ -65,6 +65,13 @@ platform.
  Notable changes
  ===============
  +Mining
  +------
  +
  +- Calls to `getblocktemplate` will fail if the segwit rule is not specified.
  + Calling `getblocktemplate` without segwit specified is almost certainly
  + a misconfiguration since doing so results in lower rewards for the miner.
  +
  Command line option changes
  ---------------------------
  @@ -182,6 +189,8 @@ in the Low-level Changes section below.
  P2SH-P2WPKH, and P2SH-P2WSH. Requests for P2WSH and P2SH-P2WSH accept
  an additional `witnessscript` parameter.
  +- See the [Mining](#mining) section for changes to `getblocktemplate`.
  +
  Low-level changes
  =================
  