chore: remove standard from dev dependencies (#272)

Author: okuramasafumi

activeagent.gemspec

@@ -31,7 +31,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "anthropic", "~> 1.12"
   spec.add_development_dependency "openai", "~> 0.34"
 
-  spec.add_development_dependency "standard"
   spec.add_development_dependency "rubocop-rails-omakase"
 
   spec.add_development_dependency "capybara", "~> 3.40"