CI: github actions: -Wno-deprecated-declarations with OpenSSL 3.0.0

Disable the deprecated functions warning when building with openssl
3.0.0 alpha. This will need to be reverted once haproxy is ported to the
new API.

(cherry picked from commit 64d6c09e54f5deed060ece04ad53a3f5298c0a96)
Signed-off-by: William Lallemand <wlallemand@haproxy.org>
diff --git a/.github/matrix.py b/.github/matrix.py
index dd2a61d..b75614c 100644
--- a/.github/matrix.py
+++ b/.github/matrix.py
@@ -112,6 +112,8 @@
         flags = ["USE_OPENSSL=1"]
         if ssl == "BORINGSSL=yes":
             flags.append("USE_QUIC=1")
+        if ssl == "OPENSSL_VERSION=3.0.0-alpha17":
+            flags.append('DEBUG_CFLAGS="-g -Wno-deprecated-declarations"')
         if ssl != "stock":
             flags.append("SSL_LIB=${HOME}/opt/lib")
             flags.append("SSL_INC=${HOME}/opt/include")