Bump govuk_app_config from 4.12.0 to 4.13.0

Bumps [govuk_app_config](https://github.com/alphagov/govuk_app_config) from 4.12.0 to 4.13.0.
- [Release notes](https://github.com/alphagov/govuk_app_config/releases)
- [Changelog](https://github.com/alphagov/govuk_app_config/blob/main/CHANGELOG.md)
- [Commits](alphagov/govuk_app_config@v4.12.0...v4.13.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -124,7 +124,7 @@ GEM
     globalid (1.0.0)
       activesupport (>= 5.0)
     govuk_ab_testing (2.4.2)
-    govuk_app_config (4.12.0)
+    govuk_app_config (4.13.0)
       logstasher (~> 2.1)
       plek (>= 4, < 6)
       prometheus_exporter (~> 2.0)
@@ -235,7 +235,7 @@ GEM
     puma (6.0.2)
       nio4r (~> 2.0)
     racc (1.6.2)
-    rack (2.2.5)
+    rack (2.2.6)
     rack-proxy (0.7.4)
       rack
     rack-test (2.0.2)