Bump govuk_design_system_formbuilder from 5.4.1 to 5.5.0 (#827)

Bumps [govuk_design_system_formbuilder](https://github.com/x-govuk/govuk-form-builder) from 5.4.1 to 5.5.0.
- [Release notes](https://github.com/x-govuk/govuk-form-builder/releases)
- [Commits](x-govuk/govuk-form-builder@v5.4.1...v5.5.0)

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

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

Gemfile.lock

@@ -242,7 +242,7 @@ GEM
       rake (>= 10.0)
     globalid (1.2.1)
       activesupport (>= 6.1)
-    govuk_design_system_formbuilder (5.4.1)
+    govuk_design_system_formbuilder (5.5.0)
       actionview (>= 6.1)
       activemodel (>= 6.1)
       activesupport (>= 6.1)