CI: github: switch to wolfssl git-c4b77ad for new PR

The "dynamic-certs-n-ciphers" PR was just merged, lets build the wolfssl
git instead of the 5.6.4 version, so we could test the feature.

.github/matrix.py

@@ -194,7 +194,7 @@ def main(ref_name):
             "OPENSSL_VERSION=1.0.2u",
             "OPENSSL_VERSION=1.1.1s",
             "QUICTLS=yes",
-            "WOLFSSL_VERSION=5.6.4",
+            "WOLFSSL_VERSION=git-c4b77ad",
             "AWS_LC_VERSION=1.16.0",
             # "BORINGSSL=yes",
         ]