fix: packages/@vue/cli-plugin-eslint/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-ACORN-559469

Author: snyk-bot

packages/@vue/cli-plugin-eslint/package.json

@@ -24,8 +24,8 @@
   "dependencies": {
     "@vue/cli-shared-utils": "^3.0.1",
     "babel-eslint": "^8.2.5",
-    "eslint": "^4.19.1",
+    "eslint": "^6.0.0",
     "eslint-loader": "^2.0.0",
-    "eslint-plugin-vue": "^4.5.0"
+    "eslint-plugin-vue": "^6.1.0"
   }
 }