Build(deps): bump govuk_app_config from 9.17.14 to 9.17.15

Bumps [govuk_app_config](https://github.com/alphagov/govuk_app_config) from 9.17.14 to 9.17.15.
- [Changelog](https://github.com/alphagov/govuk_app_config/blob/main/CHANGELOG.md)
- [Commits](alphagov/govuk_app_config@v9.17.14...v9.17.15)

---
updated-dependencies:
- dependency-name: govuk_app_config
  dependency-version: 9.17.15
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -179,7 +179,7 @@ GEM
       nokogiri (~> 1.12)
       rinku (~> 2.0)
       sanitize (>= 6, < 8)
-    govuk_app_config (9.17.14)
+    govuk_app_config (9.17.15)
       logstasher (~> 2.1)
       opentelemetry-exporter-otlp (>= 0.25, < 0.31)
       opentelemetry-instrumentation-all (>= 0.39.1, < 0.79.0)