utils: switch to standard library min and max functions (#4218)

These functions were added in Go 1.21.

internal/handshake/updatable_aead.go

@@ -172,7 +172,7 @@ func (a *updatableAEAD) Open(dst, src []byte, rcvTime time.Time, pn protocol.Pac
 		}
 	}
 	if err == nil {
-		a.highestRcvdPN = utils.Max(a.highestRcvdPN, pn)
+		a.highestRcvdPN = max(a.highestRcvdPN, pn)
 	}
 	return dec, err
 }