chore(deps): update dependency eslint-config-prettier to v4 (#370)

Author: renovate[bot]

package.json

@@ -91,7 +91,7 @@
     "bignumber.js": "^8.0.0",
     "codecov": "^3.0.4",
     "eslint": "^5.4.0",
-    "eslint-config-prettier": "^3.1.0",
+    "eslint-config-prettier": "^4.0.0",
     "eslint-plugin-node": "^8.0.0",
     "eslint-plugin-prettier": "^3.0.0",
     "google-proto-files": "^0.18.0",