CI: switch to Fastly CDN to download LibreSSL

OpenBSD ftp is down, let us switch to mirror

(cherry picked from commit 156c4b3439023beed151bd4e36b65a6583d14027)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit cd2c6080954943ead7465f82c0bca54f67402f1a)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit c7292a72a6dc97ad125c2e573b8f093046d80a38)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/.github/matrix.py b/.github/matrix.py
index abd6caf..e03358b 100644
--- a/.github/matrix.py
+++ b/.github/matrix.py
@@ -44,7 +44,9 @@
     return "OPENSSL_VERSION={}".format(latest_tag[8:])
 
 def determine_latest_libressl(ssl):
-    libressl_download_list = urllib.request.urlopen("http://ftp.openbsd.org/pub/OpenBSD/LibreSSL/")
+    libressl_download_list = urllib.request.urlopen(
+        "https://cdn.openbsd.org/pub/OpenBSD/LibreSSL/"
+    )
     for line in libressl_download_list.readlines():
         decoded_line = line.decode("utf-8")
         if "libressl-" in decoded_line and ".tar.gz.asc" in decoded_line: