build(deps): update dependency govuk-prototype-kit to ^13.18.1

Author: renovate[bot]

package-lock.json

@@ -143,7 +143,7 @@
     "eslint-plugin-n": "^16.6.2",
     "eslint-plugin-promise": "^6.6.0",
     "glob": "^11.0.3",
-    "govuk-prototype-kit": "^13.18.0",
+    "govuk-prototype-kit": "^13.18.1",
     "gray-matter": "^4.0.3",
     "gulp": "^5.0.1",
     "gulp-cache": "^1.1.3",