Bump @x-govuk/govuk-eleventy-plugin from 6.0.3 to 6.0.4 (#286)

Bumps [@x-govuk/govuk-eleventy-plugin](https://github.com/x-govuk/govuk-eleventy-plugin) from 6.0.3 to 6.0.4.
- [Release notes](https://github.com/x-govuk/govuk-eleventy-plugin/releases)
- [Commits](x-govuk/govuk-eleventy-plugin@v6.0.3...v6.0.4)

---
updated-dependencies:
- dependency-name: "@x-govuk/govuk-eleventy-plugin"
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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package.json

@@ -26,7 +26,7 @@
   },
   "dependencies": {
     "@11ty/eleventy": "^2.0.1",
-    "@x-govuk/govuk-eleventy-plugin": "^6.0.3",
+    "@x-govuk/govuk-eleventy-plugin": "^6.0.4",
     "http-server": "^14.1.1",
     "rimraf": "^5.0.5",
     "sass": "^1.69.7"