chore(deps): bump rack-session from 2.0.0 to 2.1.0 in /builder

Bumps [rack-session](https://github.com/rack/rack-session) from 2.0.0 to 2.1.0.
- [Release notes](https://github.com/rack/rack-session/releases)
- [Changelog](https://github.com/rack/rack-session/blob/v2.1.0/releases.md)
- [Commits](rack/rack-session@v2.0.0...v2.1.0)

---
updated-dependencies:
- dependency-name: rack-session
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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

builder/Gemfile.lock

@@ -229,7 +229,8 @@ GEM
       rack (>= 2.0.0)
     rack-proxy (0.7.7)
       rack
-    rack-session (2.0.0)
+    rack-session (2.1.0)
+      base64 (>= 0.1.0)
       rack (>= 3.0.0)
     rack-test (2.2.0)
       rack (>= 1.3)