fix missing '#[cfg(unix)]'

tokio-postgres/src/config.rs

@@ -236,6 +236,7 @@ impl Config {
     /// Adds a Unix socket host to the configuration.
     ///
     /// Unlike `host`, this method allows non-UTF8 paths.
+    #[cfg(unix)]
     pub fn host_path<T>(&mut self, host: T) -> &mut Config
     where
         T: AsRef<Path>,