Bump slim/psr7 from 1.7.1 to 1.8.0

Bumps [slim/psr7](https://github.com/slimphp/Slim-Psr7) from 1.7.1 to 1.8.0.
- [Release notes](https://github.com/slimphp/Slim-Psr7/releases)
- [Commits](slimphp/Slim-Psr7@1.7.1...1.8.0)

---
updated-dependencies:
- dependency-name: slim/psr7
  dependency-version: 1.8.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]