Update dependency eslint to v7

Author: renovate-bot

frontend/package.json

@@ -38,7 +38,7 @@
     "@vue/test-utils": "2.0.0-rc.10",
     "babel-jest": "26.6.3",
     "chromedriver": "91.0.1",
-    "eslint": "6.8.0",
+    "eslint": "7.30.0",
     "eslint-plugin-vue": "7.13.0",
     "geckodriver": "2.0.1",
     "node-sass": "6.0.1",