kv.go: Fixed []byte to string conversion syntax in comment

clientv3/kv.go

@@ -32,7 +32,7 @@ type KV interface {
 	// Put puts a key-value pair into etcd.
 	// Note that key,value can be plain bytes array and string is
 	// an immutable representation of that bytes array.
-	// To get a string of bytes, do string([]byte(0x10, 0x20)).
+	// To get a string of bytes, do string([]byte{0x10, 0x20}).
 	Put(ctx context.Context, key, val string, opts ...OpOption) (*PutResponse, error)
 
 	// Get retrieves keys.