Update steep requirement from ~> 1.7.0 to ~> 1.7.1 (#561)

Updates the requirements on [steep](https://github.com/soutaro/steep) to permit the latest version.

Updates `steep` to 1.7.1
- [Release notes](https://github.com/soutaro/steep/releases)
- [Changelog](https://github.com/soutaro/steep/blob/master/CHANGELOG.md)
- [Commits](soutaro/steep@v1.7.0...v1.7.1)

---
updated-dependencies:
- dependency-name: steep
  dependency-type: direct:development
  dependency-group: rbs-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile

@@ -14,7 +14,7 @@ end
 group(:development) do
   gem('debug', '~> 1.9.2', require: false)
   gem('rbs', '~> 3.5.1', require: false)
-  gem('steep', '~> 1.7.0', require: false)
+  gem('steep', '~> 1.7.1', require: false)
   gem('benchmark-ips', '~> 2.13.0', require: false)
   gem('stackprof')
   gem('yard', '~> 0.9.36', require: false)