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