Bump rack-session from 2.1.1 to 2.1.2 in /spec/dummy (#46)

Bumps [rack-session](https://github.com/rack/rack-session) from 2.1.1 to 2.1.2.
- [Release notes](https://github.com/rack/rack-session/releases)
- [Changelog](https://github.com/rack/rack-session/blob/main/releases.md)
- [Commits](https://github.com/rack/rack-session/compare/v2.1.1...v2.1.2)

---
updated-dependencies:
- dependency-name: rack-session
  dependency-version: 2.1.2
  dependency-type: indirect
...

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