message: remove unused global constant
diff: pub const SEQ_NO: i32 = 1;
  pub const PROTOCOL_VERSION: usize = 2;
  -pub const WALLET: &'static str = "wallet_1"; // FIXME never use global names
  pub const TYPE: &'static str = "default";
  pub const INMEM_TYPE: &'static str = "inmem";
  pub const SIGNATURE_TYPE: &'static str = "CL";
  