change doc

Author: qiulaidongfeng

src/crypto/rsa/rsa.go

@@ -59,7 +59,7 @@ func (pub *PublicKey) Size() int {
 
 // Equal reports whether pub and x have the same value.
 //
-// x must be a pointer to [PublicKey]
+// applie only to [*PublicKey], returns false in other cases.
 func (pub *PublicKey) Equal(x crypto.PublicKey) bool {
 	xx, ok := x.(*PublicKey)
 	if !ok {