Update dependency @ministryofjustice/frontend to v6

Author: renovate[bot]

package-lock.json

@@ -8,7 +8,7 @@
   "name": "govuk-prototype-kit",
   "dependencies": {
     "@govuk-prototype-kit/step-by-step": "2.2.3",
-    "@ministryofjustice/frontend": "^2.0.0",
+    "@ministryofjustice/frontend": "^6.0.0",
     "govuk-frontend": "5.13.0",
     "govuk-prototype-kit": "13.18.1",
     "hmrc-frontend": "^6.0.0",