[ruby/logger] Add missing closing "

https://github.com/ruby/logger/commit/b4b3caae40

lib/logger.gemspec

@@ -21,7 +21,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
   
-  spec.required_ruby_version = ">= 2.3.0
+  spec.required_ruby_version = ">= 2.3.0"
 
   spec.add_development_dependency "bundler", ">= 0"
   spec.add_development_dependency "rake", "~> 10.0"