Bump rack from 2.1.2 to 2.2.3 in /builder

Bumps [rack](https://github.com/rack/rack) from 2.1.2 to 2.2.3. - [Release notes](https://github.com/rack/rack/releases) - [Changelog](https://github.com/rack/rack/blob/master/CHANGELOG.md) - [Commits](rack/rack@2.1.2...2.2.3) Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

builder/Gemfile.lock

@@ -87,7 +87,7 @@ GEM
  nokogiri (1.10.8)
  mini_portile2 (~> 2.4.0)
  puma (3.12.4)
- rack (2.1.2)
+ rack (2.2.3)
  rack-proxy (0.6.5)
  rack
  rack-test (1.1.0)