Bump govuk_design_system_formbuilder from 5.1.0 to 5.4.0 (#758)

Bumps [govuk_design_system_formbuilder](https://github.com/x-govuk/govuk-form-builder) from 5.1.0 to 5.4.0.
- [Release notes](https://github.com/x-govuk/govuk-form-builder/releases)
- [Commits](x-govuk/govuk-form-builder@v5.1.0...v5.4.0)

---
updated-dependencies:
- dependency-name: govuk_design_system_formbuilder
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -165,7 +165,7 @@ GEM
       html-attributes-utils (~> 1.0.0, >= 1.0.0)
       pagy (~> 6.0)
       view_component (>= 3.9, < 3.11)
-    govuk_design_system_formbuilder (5.1.0)
+    govuk_design_system_formbuilder (5.4.0)
       actionview (>= 6.1)
       activemodel (>= 6.1)
       activesupport (>= 6.1)