message: Update docs: GetBlock error code 3
diff: @@ -134,8 +134,14 @@ Possible Stateful Validation Errors
  "1", "Could not get block", "Internal error happened", "Try again or contact developers"
  "2", "No such permissions", "Query's creator does not have a permission to get block", "Grant `can_get_block <../maintenance/permissions.html#can-get-blocks>`__ permission"
  + "3", "Invalid signatures", "Signatures of this query did not pass validation", "Add more signatures and make sure query's signatures are a subset of account's signatories"
  "3", "Invalid height", "Supplied height is not uint_64 or greater than the ledger's height", "Check the height and try again"
  +.. note::
  + Error code 3 is ambiguos for this method.
  + It indicates either invalid signatories or invalid height.
  + Use this method with `height = 1` (first block is always present) to check for invalid signatories.
  +
  Get Signatories
  ^^^^^^^^^^^^^^^
  