Update html-webpack-plugin (#6361)

Author: Aftabnack

packages/react-scripts/package.json

@@ -46,7 +46,7 @@
     "eslint-plugin-react": "7.12.4",
     "file-loader": "2.0.0",
     "fs-extra": "7.0.1",
-    "html-webpack-plugin": "4.0.0-alpha.2",
+    "html-webpack-plugin": "4.0.0-beta.5",
     "identity-obj-proxy": "3.0.0",
     "jest": "23.6.0",
     "jest-pnp-resolver": "1.0.2",