Update solargraph requirement from ~> 0.57.0 to ~> 0.58.1

Updates the requirements on [solargraph](https://github.com/castwide/solargraph) to permit the latest version.
- [Changelog](https://github.com/castwide/solargraph/blob/master/CHANGELOG.md)
- [Commits](https://github.com/castwide/solargraph/commits)

---
updated-dependencies:
- dependency-name: solargraph
  dependency-version: 0.58.1
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile

@@ -11,7 +11,7 @@ group :development do
   gem "debug", "~> 1.8"
   gem "rake", "~> 13.3.0"
   gem "semver2", "~> 3.4"
-  gem "solargraph", "~> 0.57.0"
+  gem "solargraph", "~> 0.58.1"
 end
 
 group :test do