message: Remove unknown lint allow
  Merge this once everyone is on rust 1.40 and the unused_self warning is
  understood.
  Closes
diff: @@ -54,8 +54,7 @@ pub struct Aead {
  }
  // TODO(mt) move unused_self once https://github.com/rust-lang/rust-clippy/issues/5053 is fixed
  -// TODO(mt) remove unknown_clippy_lints once we are on 1.40 consistently
  -#[allow(clippy::unused_self, clippy::unknown_clippy_lints)]
  +#[allow(clippy::unused_self)]
  impl Aead {
  pub fn new(version: Version, cipher: Cipher, secret: &SymKey, prefix: &str) -> Res<Self> {
  let s: *mut PK11SymKey = **secret;
  