Update test-unit requirement from = 3.5.7 to = 3.5.8 (#2760)

Updates the requirements on [test-unit](https://github.com/test-unit/test-unit) to permit the latest version.
- [Release notes](https://github.com/test-unit/test-unit/releases)
- [Commits](test-unit/test-unit@3.5.7...3.5.8)

---
updated-dependencies:
- dependency-name: test-unit
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Gemfile.lock

@@ -19,7 +19,7 @@ GEM
  parallel (1.22.1)
  parser (3.2.2.0)
  ast (~> 2.4.1)
- power_assert (2.0.2)
+ power_assert (2.0.3)
  pry (0.14.2)
  coderay (~> 1.1)
  method_source (~> 1.0)
@@ -50,7 +50,7 @@ GEM
  simplecov_json_formatter (~> 0.1)
  simplecov-html (0.12.3)
  simplecov_json_formatter (0.1.4)
- test-unit (3.5.7)
+ test-unit (3.5.8)
  power_assert
  timecop (0.9.6)
  unicode-display_width (2.4.2)
@@ -68,7 +68,7 @@ DEPENDENCIES
  rubocop-minitest (= 0.30.0)
  rubocop-rake (= 0.6.0)
  simplecov (= 0.22.0)
- test-unit (= 3.5.7)
+ test-unit (= 3.5.8)
  timecop (= 0.9.6)
  yard (= 0.9.34)
 

faker.gemspec

@@ -36,7 +36,7 @@ Gem::Specification.new do |spec|
  spec.add_development_dependency('rubocop-minitest', '0.30.0')
  spec.add_development_dependency('rubocop-rake', '0.6.0')
  spec.add_development_dependency('simplecov', '0.22.0')
- spec.add_development_dependency('test-unit', '3.5.7')
+ spec.add_development_dependency('test-unit', '3.5.8')
  spec.add_development_dependency('timecop', '0.9.6')
  spec.add_development_dependency('yard', '0.9.34')
 end