Update simplecov to version 0.21.2

Author: depfu[bot]

pactas_itero.gemspec

@@ -32,6 +32,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rspec", "~> 3.11.0"
   spec.add_development_dependency("rubocop", "~> 1.25.1")
   spec.add_development_dependency("rubocop-performance", "~> 1.13.2")
-  spec.add_development_dependency("simplecov", "~> 0.16.1")
+  spec.add_development_dependency("simplecov", "~> 0.21.2")
   spec.add_development_dependency("webmock", "~> 3.3")
 end