header.go
func (h *ResponseHeader) Del(key string) {
	k := getHeaderKeyBytes(&h.bufKV, key, h.disableNormalizing)
	h.del(k)
}
func (h *ResponseHeader) Del(key string) {
	k := getHeaderKeyBytes(&h.bufKV, key, h.disableNormalizing)
	h.del(k)
}
// Del deletes header with the given key.