CI: Github Actions: switch to LibreSSL-3.3.3

stable LibreSSL-3.3.3 released, let us switch to it
diff --git a/.github/matrix.py b/.github/matrix.py
index 22c33f0..577ad5b 100644
--- a/.github/matrix.py
+++ b/.github/matrix.py
@@ -105,7 +105,7 @@
         "stock",
         "OPENSSL_VERSION=1.0.2u",
         "LIBRESSL_VERSION=2.9.2",
-        "LIBRESSL_VERSION=3.2.5",
+        "LIBRESSL_VERSION=3.3.3",
         "BORINGSSL=yes",
     ]:
         flags = ["USE_OPENSSL=1"]