Bump @x-govuk/govuk-eleventy-plugin from 6.0.4 to 6.2.1

Bumps [@x-govuk/govuk-eleventy-plugin](https://github.com/x-govuk/govuk-eleventy-plugin) from 6.0.4 to 6.2.1.
- [Release notes](https://github.com/x-govuk/govuk-eleventy-plugin/releases)
- [Commits](x-govuk/govuk-eleventy-plugin@v6.0.4...v6.2.1)

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

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -26,7 +26,7 @@
   },
   "dependencies": {
     "@11ty/eleventy": "^2.0.1",
-    "@x-govuk/govuk-eleventy-plugin": "^6.0.4",
+    "@x-govuk/govuk-eleventy-plugin": "^6.2.1",
     "http-server": "^14.1.1",
     "rimraf": "^5.0.5",
     "sass": "^1.70.0"