pin version

Author: darrenscerri

packages/react-scripts/package.json

@@ -33,7 +33,7 @@
     "css-loader": "0.28.7",
     "dotenv": "4.0.0",
     "dotenv-expand": "4.0.1",
-    "duplicate-package-checker-webpack-plugin": "^2.1.0",
+    "duplicate-package-checker-webpack-plugin": "2.1.0",
     "eslint": "4.10.0",
     "eslint-config-react-app": "^2.0.1",
     "eslint-loader": "1.9.0",