Use @babel/eslint-parser instead of babel-eslint

Not sure why babel-eslint was used when it was missing from
package-lock. Use the newer NPM package¹, which is already installed by
another dependency.

¹ https://www.npmjs.com/package/babel-eslint

react-app/.eslintrc.json

@@ -22,7 +22,7 @@
     ]
   },
   "plugins": ["react", "import", "jsx-a11y"],
-  "parser": "react-scripts/node_modules/babel-eslint",
+  "parser": "@babel/eslint-parser",
   "parserOptions": {
     "ecmaVersion": 2018,
     "sourceType": "module",