CI: switch to the "latest" LibreSSL

LibreSSL-3.6.0 had some regression, it was fixed in 3.6.1, let us
switch back to the latest LibreSSL available

(cherry picked from commit 70b2c72687ae6e33d2f81147837d4d7c38ef3b9f)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit a7c11202a88145dd5abece3203da615b87feb305)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit aac6ff14dc8f5a5f951cd8285fdc56cf4f1c6f33)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/.github/matrix.py b/.github/matrix.py
index 3b4ac0a..14d3b5e 100644
--- a/.github/matrix.py
+++ b/.github/matrix.py
@@ -127,7 +127,7 @@
         "stock",
         "OPENSSL_VERSION=1.0.2u",
         "OPENSSL_VERSION=latest",
-        "LIBRESSL_VERSION=3.5.3",
+        "LIBRESSL_VERSION=latest",
 #        "BORINGSSL=yes",
     ]:
         flags = ["USE_OPENSSL=1"]