minor: fixed debug message on config.json version mismatch

src/main.rs

@@ -314,8 +314,8 @@ mod conf {
                     eprintln!(
                         concat!("Configuration file has outdated version.\n",
                         "Expected version field to be {} but got {}."),
+                        config_version(),
                         old_version,
-                        config_version()
                     );
                 }
                 ConfigParseError::ServeDirNotExists(dir) => {