Update test-unit requirement from = 3.3.7 to = 3.3.8 (#2223)

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@3.3.7...3.3.8)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Gemfile.lock

@@ -44,7 +44,7 @@ GEM
  json (>= 1.8, < 3)
  simplecov-html (~> 0.10.0)
  simplecov-html (0.10.2)
- test-unit (3.3.7)
+ test-unit (3.3.8)
  power_assert
  timecop (0.9.2)
  unicode-display_width (1.7.0)
@@ -60,7 +60,7 @@ DEPENDENCIES
  rake (= 13.0.1)
  rubocop (= 1.1.0)
  simplecov (= 0.17.1)
- test-unit (= 3.3.7)
+ test-unit (= 3.3.8)
  timecop (= 0.9.2)
  yard (= 0.9.25)
 

faker.gemspec

@@ -34,7 +34,7 @@ Gem::Specification.new do |spec|
  spec.add_development_dependency('rake', '13.0.1')
  spec.add_development_dependency('rubocop', '1.1.0')
  spec.add_development_dependency('simplecov', '0.17.1')
- spec.add_development_dependency('test-unit', '3.3.7')
+ spec.add_development_dependency('test-unit', '3.3.8')
  spec.add_development_dependency('timecop', '0.9.2')
  spec.add_development_dependency('yard', '0.9.25')
 end