[http_request] Pass collect_headers by const reference instead of by value (#11494)

esphome/components/http_request/http_request_host.cpp

@@ -20,7 +20,7 @@ static const char *const TAG = "http_request.host";
 std::shared_ptr<HttpContainer> HttpRequestHost::perform(const std::string &url, const std::string &method,
                                                         const std::string &body,
                                                         const std::list<Header> &request_headers,
-                                                        std::set<std::string> response_headers) {
+                                                        const std::set<std::string> &response_headers) {
   if (!network::is_connected()) {
     this->status_momentary_error("failed", 1000);
     ESP_LOGW(TAG, "HTTP Request failed; Not connected to network");