fix(deps): update dependency @netlify/functions to v5

Author: renovate[bot]

plugin/package-lock.json

@@ -40,7 +40,7 @@
     "prepare": "npm run build"
   },
   "dependencies": {
-    "@netlify/functions": "^1.6.0",
+    "@netlify/functions": "^5.1.0",
     "@netlify/ipx": "^1.4.6",
     "abortcontroller-polyfill": "^1.7.3",
     "chalk": "^4.1.2",