Remove unneeded explicit reference

Clippy emits:

  warning: this expression creates a reference which is immediately
  dereferenced by the compiler

Remove the explicit reference.

src/ecdh.rs

@@ -176,7 +176,7 @@ impl ::serde::Serialize for SharedSecret {
             let mut buf = [0u8; SHARED_SECRET_SIZE * 2];
             s.serialize_str(crate::to_hex(&self.0, &mut buf).expect("fixed-size hex serialization"))
         } else {
-            s.serialize_bytes(&self.as_ref()[..])
+            s.serialize_bytes(self.as_ref())
         }
     }
 }

src/key.rs

@@ -431,7 +431,7 @@ impl PublicKey {
     #[cfg(feature = "global-context")]
     #[cfg_attr(docsrs, doc(cfg(feature = "global-context")))]
     pub fn from_secret_key_global(sk: &SecretKey) -> PublicKey {
-        PublicKey::from_secret_key(&SECP256K1, sk)
+        PublicKey::from_secret_key(SECP256K1, sk)
     }
 
     /// Creates a public key directly from a slice.
@@ -1621,7 +1621,7 @@ pub mod serde_keypair {
         let secret_key = SecretKey::deserialize(deserializer)?;
 
         Ok(KeyPair::from_secret_key(
-            &crate::SECP256K1,
+            crate::SECP256K1,
             &secret_key,
         ))
     }

src/lib.rs

@@ -729,10 +729,10 @@ mod tests {
 
         assert_eq!(
             ecdsa::Signature::from_der(&byte_str).expect("byte str decode"),
-            ecdsa::Signature::from_str(&hex_str).expect("byte str decode")
+            ecdsa::Signature::from_str(hex_str).expect("byte str decode")
         );
 
-        let sig = ecdsa::Signature::from_str(&hex_str).expect("byte str decode");
+        let sig = ecdsa::Signature::from_str(hex_str).expect("byte str decode");
         assert_eq!(&sig.to_string(), hex_str);
         assert_eq!(&format!("{:?}", sig), hex_str);
 
@@ -759,7 +759,7 @@ mod tests {
 
         // 71 byte signature
         let hex_str = "30450221009d0bad576719d32ae76bedb34c774866673cbde3f4e12951555c9408e6ce774b02202876e7102f204f6bfee26c967c3926ce702cf97d4b010062e193f763190f6776";
-        let sig = ecdsa::Signature::from_str(&hex_str).expect("byte str decode");
+        let sig = ecdsa::Signature::from_str(hex_str).expect("byte str decode");
         assert_eq!(&format!("{}", sig), hex_str);
     }
 
@@ -1026,7 +1026,7 @@ mod tests {
         let msg = Message::from_slice(&msg_data).unwrap();
 
         // Check usage as explicit parameter
-        let pk = PublicKey::from_secret_key(&SECP256K1, &sk);
+        let pk = PublicKey::from_secret_key(SECP256K1, &sk);
 
         // Check usage as self
         let sig = SECP256K1.sign_ecdsa(&msg, &sk);