[ruby/csv] CI: Stop coverage mesurement

https://github.com/ruby/csv/commit/5ff3b95018

lib/csv/csv.gemspec

@@ -60,5 +60,4 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "bundler"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "benchmark_driver"
-  spec.add_development_dependency "simplecov"
 end