CI: github actions: add OpenSSL-3.0.0 builds

OpenSSL-3.0.0 is getting close to its release, let us add it to build matrix

(cherry picked from commit c3f28a38d261de052143145e87c7292357d40692)
Signed-off-by: William Lallemand <wlallemand@haproxy.org>
diff --git a/.github/matrix.py b/.github/matrix.py
index 9900314..dd2a61d 100644
--- a/.github/matrix.py
+++ b/.github/matrix.py
@@ -104,6 +104,7 @@
     for ssl in [
         "stock",
         "OPENSSL_VERSION=1.0.2u",
+        "OPENSSL_VERSION=3.0.0-alpha17",
         "LIBRESSL_VERSION=2.9.2",
         "LIBRESSL_VERSION=3.3.3",
 #        "BORINGSSL=yes",