Bump slim/psr7 from 1.6.1 to 1.7.0

Bumps [slim/psr7](https://github.com/slimphp/Slim-Psr7) from 1.6.1 to 1.7.0.
- [Release notes](https://github.com/slimphp/Slim-Psr7/releases)
- [Commits](slimphp/Slim-Psr7@1.6.1...1.7.0)

---
updated-dependencies:
- dependency-name: slim/psr7
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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