Bump rack from 2.2.9 to 3.1.4

Bumps [rack](https://github.com/rack/rack) from 2.2.9 to 3.1.4.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.9...v3.1.4)

---
updated-dependencies:
- dependency-name: rack
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Gemfile

@@ -7,7 +7,7 @@ gem "govuk_app_config", "~> 9.12.0"
 gem "nokogiri", "1.16.6"
 gem "optic14n", "2.1.0" # Ideally version should be synced with Transition
 gem "pg"
-gem "rack", "~> 2.2.9"
+gem "rack", "~> 3.1.4"
 gem "rake", "13.2.1"
 
 group :development do

Gemfile.lock

@@ -331,16 +331,16 @@ GEM
     puma (6.4.2)
       nio4r (~> 2.0)
     racc (1.8.0)
-    rack (2.2.9)
+    rack (3.1.4)
     rack-proxy (0.7.7)
       rack
-    rack-session (1.0.2)
-      rack (< 3)
+    rack-session (2.0.0)
+      rack (>= 3.0.0)
     rack-test (2.1.0)
       rack (>= 1.3)
-    rackup (1.0.0)
-      rack (< 3)
-      webrick
+    rackup (2.1.0)
+      rack (>= 3)
+      webrick (~> 1.8)
     rails-dom-testing (2.2.0)
       activesupport (>= 5.0.0)
       minitest
@@ -459,7 +459,7 @@ DEPENDENCIES
   optic14n (= 2.1.0)
   pg
   pry
-  rack (~> 2.2.9)
+  rack (~> 3.1.4)
   rack-test (= 2.1.0)
   rake (= 13.2.1)
   rspec