Bump govuk_app_config from 4.8.0 to 4.9.0

Bumps [govuk_app_config](https://github.com/alphagov/govuk_app_config) from 4.8.0 to 4.9.0.
- [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@v4.8.0...v4.9.0)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -138,10 +138,12 @@ GEM
       warden-oauth2 (~> 0.0.1)
     globalid (1.0.0)
       activesupport (>= 5.0)
-    govuk_app_config (4.8.0)
+    govuk_app_config (4.9.0)
       logstasher (~> 2.1)
+      plek (~> 4)
       prometheus_exporter (~> 2.0)
       puma (~> 5.6)
+      rack-proxy (~> 0.7)
       sentry-rails (~> 5.3)
       sentry-ruby (~> 5.3)
       statsd-ruby (~> 1.5)
@@ -267,13 +269,15 @@ GEM
       coderay (~> 1.1)
       method_source (~> 1.0)
     public_suffix (5.0.0)
-    puma (5.6.4)
+    puma (5.6.5)
       nio4r (~> 2.0)
     raabro (1.4.0)
     racc (1.6.0)
     rack (2.2.4)
     rack-protection (2.2.2)
       rack
+    rack-proxy (0.7.2)
+      rack
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (7.0.3.1)