Bump rack from 3.1.7 to 3.1.8

Bumps [rack](https://github.com/rack/rack) from 3.1.7 to 3.1.8.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v3.1.7...v3.1.8)

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

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

Gemfile

@@ -7,7 +7,7 @@ gem "govuk_app_config", "~> 9.14.3"
 gem "nokogiri", "1.16.7"
 gem "optic14n", "2.1.0" # Ideally version should be synced with Transition
 gem "pg"
-gem "rack", "~> 3.1.7"
+gem "rack", "~> 3.1.8"
 gem "rake", "13.2.1"
 
 group :development do

Gemfile.lock

@@ -334,7 +334,7 @@ GEM
     puma (6.4.3)
       nio4r (~> 2.0)
     racc (1.8.1)
-    rack (3.1.7)
+    rack (3.1.8)
     rack-proxy (0.7.7)
       rack
     rack-session (2.0.0)
@@ -464,7 +464,7 @@ DEPENDENCIES
   optic14n (= 2.1.0)
   pg
   pry
-  rack (~> 3.1.7)
+  rack (~> 3.1.8)
   rack-test (= 2.1.0)
   rake (= 13.2.1)
   rspec