Update dependency eslint-loader to v4

Signed-off-by: Renovate Bot <bot@renovateapp.com>

Author: renovate-bot

package-lock.json

@@ -49,7 +49,7 @@
     "classnames": "^2.2.6",
     "eslint": "^6.8.0",
     "eslint-config-airbnb": "^18.1.0",
-    "eslint-loader": "^2.2.1",
+    "eslint-loader": "^4.0.1",
     "eslint-plugin-import": "^2.20.2",
     "eslint-plugin-jsx-a11y": "^6.2.3",
     "eslint-plugin-react": "^7.19.0",