CI: github actions: update LibreSSL to 3.5.2

LibreSSL-3.5.2 was released on Apr 23nd 2022, let us switch to it
diff --git a/.github/matrix.py b/.github/matrix.py
index d070ae2..a4d1265 100755
--- a/.github/matrix.py
+++ b/.github/matrix.py
@@ -112,7 +112,7 @@
         "OPENSSL_VERSION=1.0.2u",
         "OPENSSL_VERSION=3.0.2",
         "LIBRESSL_VERSION=2.9.2",
-        "LIBRESSL_VERSION=3.5.1",
+        "LIBRESSL_VERSION=3.5.2",
         "QUICTLS=yes",
 #        "BORINGSSL=yes",
     ]: