Bump govuk_app_config from 2.8.0 to 2.8.3

Bumps [govuk_app_config](https://github.com/alphagov/govuk_app_config) from 2.8.0 to 2.8.3.
- [Release notes](https://github.com/alphagov/govuk_app_config/releases)
- [Changelog](https://github.com/alphagov/govuk_app_config/blob/master/CHANGELOG.md)
- [Commits](alphagov/govuk_app_config@v2.8.0...v2.8.3)

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

Gemfile.lock

@@ -114,11 +114,11 @@ GEM
     globalid (0.4.2)
       activesupport (>= 4.2.0)
     govuk_ab_testing (2.4.2)
-    govuk_app_config (2.8.0)
-      logstasher (>= 1.2.2, < 1.4.0)
+    govuk_app_config (2.8.3)
+      logstasher (>= 1.2.2, < 2.2.0)
       sentry-raven (~> 3.1.1)
-      statsd-ruby (~> 1.4.0)
-      unicorn (>= 5.4, < 5.8)
+      statsd-ruby (~> 1.5.0)
+      unicorn (>= 5.4, < 5.9)
     govuk_publishing_components (23.12.2)
       govuk_app_config
       kramdown
@@ -160,10 +160,8 @@ GEM
       rexml
     link_header (0.0.8)
     log4r (1.1.10)
-    logstash-event (1.2.02)
-    logstasher (1.3.0)
-      activesupport (>= 4.0)
-      logstash-event (~> 1.2.0)
+    logstasher (2.1.5)
+      activesupport (>= 5.2)
       request_store
     loofah (2.8.0)
       crass (~> 1.0.2)
@@ -335,7 +333,7 @@ GEM
       actionpack (>= 4.0)
       activesupport (>= 4.0)
       sprockets (>= 3.0.0)
-    statsd-ruby (1.4.0)
+    statsd-ruby (1.5.0)
     thor (1.0.1)
     thread_safe (0.3.6)
     tilt (2.0.10)
@@ -347,7 +345,7 @@ GEM
       unf_ext
     unf_ext (0.0.7.7)
     unicode-display_width (1.7.0)
-    unicorn (5.7.0)
+    unicorn (5.8.0)
       kgio (~> 2.6)
       raindrops (~> 0.7)
     webdrivers (4.4.1)