Avoid using CURLPIPE_HTTP1 in php7.4+

src/Composer/Util/Http/CurlDownloader.php

@@ -74,7 +74,7 @@ class CurlDownloader
 
         $this->multiHandle = $mh = curl_multi_init();
         if (function_exists('curl_multi_setopt')) {
-            curl_multi_setopt($mh, CURLMOPT_PIPELINING, /*CURLPIPE_HTTP1 | CURLPIPE_MULTIPLEX*/ 3);
+            curl_multi_setopt($mh, CURLMOPT_PIPELINING, PHP_VERSION_ID >= 70400 ? /* CURLPIPE_MULTIPLEX */ 2 : /*CURLPIPE_HTTP1 | CURLPIPE_MULTIPLEX*/ 3);
             if (defined('CURLMOPT_MAX_HOST_CONNECTIONS')) {
                 curl_multi_setopt($mh, CURLMOPT_MAX_HOST_CONNECTIONS, 8);
             }