remove SKIP_ONLINE_TESTS from bug71523 test

Author: jordikroon

ext/curl/tests/bug71523.phpt

@@ -4,7 +4,6 @@ Bug #71523 (Copied handle with new option CURLOPT_HTTPHEADER crashes while curl_
 curl
 --SKIPIF--
 <?php
-if (getenv("SKIP_ONLINE_TESTS")) die("skip online test");
 if (curl_version()['version_number'] === 0x080a00) {
     // https://github.com/php/php-src/issues/15997
     die('xfail due to a libcurl bug');