[ruby/set] gemspec: This gem exposes 0 executables

This change removes unused configuration.

https://github.com/ruby/set/commit/6c2338d699

lib/set/set.gemspec

@@ -19,7 +19,5 @@ Gem::Specification.new do |spec|
   spec.files         = Dir.chdir(File.expand_path('..', __FILE__)) do
     `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) }
   end
-  spec.bindir        = "exe"
-  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 end