Update dependency gatsby-plugin-eslint to v4

Author: renovate[bot]

package.json

@@ -34,7 +34,7 @@
     "eslint-plugin-import": "^2.22.0",
     "eslint-plugin-node": "^11.1.0",
     "eslint-plugin-promise": "^4.2.1",
-    "gatsby-plugin-eslint": "^2.0.8"
+    "gatsby-plugin-eslint": "^4.0.0"
   },
   "keywords": [
     "netlify",