message: Fix payments API doc
diff: @@ -474,6 +474,7 @@ pub extern fn indy_add_request_fees(command_handle: i32,
  req_json: *const c_char,
  inputs_json: *const c_char,
  outputs_json: *const c_char,
  + extra: *const c_char,
  cb: Option<extern fn(command_handle_: i32,
  err: ErrorCode,
  req_with_fees_json: *const c_char,
  @@ -576,6 +577,7 @@ pub extern fn indy_build_payment_req(command_handle: i32,
  submitter_did: *const c_char,
  inputs_json: *const c_char,
  outputs_json: *const c_char,
  + extra: *const c_char,
  cb: Option<extern fn(command_handle_: i32,
  err: ErrorCode,
  payment_req_json: *const c_char,
  @@ -625,6 +627,7 @@ pub extern fn indy_build_mint_req(command_handle: i32,
  wallet_handle: i32,
  submitter_did: *const c_char,
  outputs_json: *const c_char,
  + extra: *const c_char,
  cb: Option<extern fn(command_handle_: i32,
  err: ErrorCode,
  mint_req_json: *const c_char,
  