chore(deps): update linters (#234)

Author: Renovate Bot

packages/google-cloud-bigquery-datatransfer/package.json

@@ -41,8 +41,8 @@
   },
   "devDependencies": {
     "codecov": "^3.5.0",
-    "eslint": "^5.16.0",
-    "eslint-config-prettier": "^4.2.0",
+    "eslint": "^6.0.0",
+    "eslint-config-prettier": "^6.0.0",
     "eslint-plugin-node": "^9.0.1",
     "eslint-plugin-prettier": "^3.1.0",
     "intelli-espower-loader": "^1.0.1",