chore(deps): bump sinatra and rack

Bumps [sinatra](https://github.com/sinatra/sinatra) and [rack](https://github.com/rack/rack). These dependencies needed to be updated together.

Updates `sinatra` from 1.0 to 3.1.0
- [Changelog](https://github.com/sinatra/sinatra/blob/main/CHANGELOG.md)
- [Commits](sinatra/sinatra@1.0...v3.1.0)

Updates `rack` from 3.0.8 to 2.2.8
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v3.0.8...v2.2.8)

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

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

buildpacks/buildpack-multi/tests/multi/Gemfile.lock

@@ -1,9 +1,18 @@
 GEM
   remote: http://rubygems.org/
   specs:
-    rack (3.0.8)
-    sinatra (1.0)
-      rack (>= 1.0)
+    mustermann (3.0.0)
+      ruby2_keywords (~> 0.0.1)
+    rack (2.2.8)
+    rack-protection (3.1.0)
+      rack (~> 2.2, >= 2.2.4)
+    ruby2_keywords (0.0.5)
+    sinatra (3.1.0)
+      mustermann (~> 3.0)
+      rack (~> 2.2, >= 2.2.4)
+      rack-protection (= 3.1.0)
+      tilt (~> 2.0)
+    tilt (2.3.0)
 
 PLATFORMS
   ruby