chore: Fix clippy lints (#881)

tonic/src/metadata/map.rs

@@ -1223,7 +1223,7 @@ impl<'a> Iterator for Iter<'a> {
 
     fn next(&mut self) -> Option<Self::Item> {
         self.inner.next().map(|item| {
-            let (ref name, value) = item;
+            let (name, value) = item;
             if Ascii::is_valid_key(name.as_str()) {
                 KeyAndValueRef::Ascii(
                     MetadataKey::unchecked_from_header_name_ref(name),
@@ -1315,7 +1315,7 @@ impl<'a> Iterator for Values<'a> {
 
     fn next(&mut self) -> Option<Self::Item> {
         self.inner.next().map(|item| {
-            let (ref name, value) = item;
+            let (name, value) = item;
             if Ascii::is_valid_key(name.as_str()) {
                 ValueRef::Ascii(MetadataValue::unchecked_from_header_value_ref(value))
             } else {

tonic/src/status.rs

@@ -498,7 +498,7 @@ impl Status {
 
         if !self.message.is_empty() {
             let to_write = Bytes::copy_from_slice(
-                Cow::from(percent_encode(&self.message().as_bytes(), ENCODING_SET)).as_bytes(),
+                Cow::from(percent_encode(self.message().as_bytes(), ENCODING_SET)).as_bytes(),
             );
 
             header_map.insert(
@@ -697,7 +697,7 @@ pub(crate) fn infer_grpc_status(
     status_code: http::StatusCode,
 ) -> Result<(), Option<Status>> {
     if let Some(trailers) = trailers {
-        if let Some(status) = Status::from_header_map(&trailers) {
+        if let Some(status) = Status::from_header_map(trailers) {
             if status.code() == Code::Ok {
                 return Ok(());
             } else {

tonic/src/transport/tls.rs

@@ -24,7 +24,7 @@ impl Certificate {
 
     /// Get a immutable reference to underlying certificate
     pub fn get_ref(&self) -> &[u8] {
-        &self.pem.as_slice()
+        self.pem.as_slice()
     }
 
     /// Get a mutable reference to underlying certificate