Upgrade node version in package.json

Author: binon

Auth/LearningHub.Nhs.Auth/package.json

@@ -23,7 +23,7 @@
     "concurrently": "^7.2.0",
     "core-js": "^3.6.5",
     "nhsuk-frontend": "^7.0.0",
-    "node": "^12.19.1"
+    "node": "^18"
   },
   "devDependencies": {
     "@babel/core": "^7.14.0",