Update standard requirement from ~> 1.12.1 to ~> 1.39.2

Updates the requirements on [standard](https://github.com/standardrb/standard) to permit the latest version.
- [Release notes](https://github.com/standardrb/standard/releases)
- [Changelog](https://github.com/standardrb/standard/blob/main/CHANGELOG.md)
- [Commits](standardrb/standard@v1.12.1...v1.39.2)

---
updated-dependencies:
- dependency-name: standard
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile

@@ -14,5 +14,5 @@ gem "yard"
 gem "mutex_m"
 
 if RUBY_VERSION >= "2.6.0"
-  gem "standard", "~> 1.12.1"
+  gem "standard", "~> 1.39.2"
 end