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
diff --git a/.github/matrix.py b/.github/matrix.py
index 9e9b395..1ff48aa 100644
--- a/.github/matrix.py
+++ b/.github/matrix.py
@@ -108,6 +108,7 @@
     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",