Update test-unit requirement from = 3.5.5 to = 3.5.6 (#2655)

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@3.5.5...3.5.6)

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

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

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 (3.1.3.0)
       ast (~> 2.4.1)
-    power_assert (2.0.1)
+    power_assert (2.0.2)
     pry (0.14.1)
       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 (3.5.5)
+    test-unit (3.5.6)
       power_assert
     timecop (0.9.6)
     unicode-display_width (2.3.0)
@@ -70,7 +70,7 @@ DEPENDENCIES
   rubocop-minitest (= 0.25.0)
   rubocop-rake (= 0.6.0)
   simplecov (= 0.21.2)
-  test-unit (= 3.5.5)
+  test-unit (= 3.5.6)
   timecop (= 0.9.6)
   yard (= 0.9.27)
 

faker.gemspec

@@ -36,7 +36,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency('rubocop-minitest', '0.25.0')
   spec.add_development_dependency('rubocop-rake', '0.6.0')
   spec.add_development_dependency('simplecov', '0.21.2')
-  spec.add_development_dependency('test-unit', '3.5.5')
+  spec.add_development_dependency('test-unit', '3.5.6')
   spec.add_development_dependency('timecop', '0.9.6')
   spec.add_development_dependency('yard', '0.9.27')
 end