keyfork-derive-openpgp: use .first() in place of .get(0)

crates/derive/keyfork-derive-openpgp/src/lib.rs

@@ -65,7 +65,7 @@ pub type Result<T, E = Error> = std::result::Result<T, E>;
 /// # Errors
 /// The function may error for any condition mentioned in [`Error`].
 pub fn derive(xprv: XPrv, keys: &[KeyFlags], userid: &UserID) -> Result<Cert> {
-    let primary_key_flags = match keys.get(0) {
+    let primary_key_flags = match keys.first() {
         Some(kf) if kf.for_certification() => kf,
         _ => return Err(Error::NotCert),
     };