Update public_suffix before fpm install. (#751)

Author: john-michaelburke

.github/workflows/main.yml

@@ -266,6 +266,7 @@ jobs:
                 build-essential \
                 libudev-dev \
                 libssl-dev
+              sudo gem install public_suffix -v 4.0.7  # This is a fix for U18.
               sudo gem install --no-document fpm
           elif [ "$RUNNER_OS" == "macOS" ]; then
               brew install capnp llvm create-dmg