```ruby
lib = File.expand_path("../lib", __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require "amakanize/version"

Gem::Specification.new do |spec|
  spec.name = "amakanize"
  spec.version = Amakanize::VERSION
  spec.authors = ["Ryo Nakamura"]
  spec.email = ["r7kamura@gmail.com"]
  spec.summary = "Utilities to canonicalize series names and author names."
  spec.homepage = "https://github.com/amakan/amakanize"
  spec.license = "MIT"

  spec.files = `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) }
  spec.bindir = "exe"
  spec.executables = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
  spec.require_paths = ["lib"]
  spec.required_ruby_version = ">= 2.2.2"

  spec.add_dependency "activesupport"
  spec.add_development_dependency "bundler"
  spec.add_development_dependency "rake", "~> 10.0"
  spec.add_development_dependency "rspec", "3.5.0"
  spec.add_development_dependency "rubocop", "0.44.1"
end
```

Remove unused configuration about executables
user
```ruby
lib = File.expand_path("../lib", __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require "amakanize/version"

Gem::Specification.new do |spec|
  spec.name = "amakanize"
  spec.version = Amakanize::VERSION
  spec.authors = ["Ryo Nakamura"]
  spec.email = ["r7kamura@gmail.com"]
  spec.summary = "Utilities to canonicalize series names and author names."
  spec.homepage = "https://github.com/amakan/amakanize"
  spec.license = "MIT"

  spec.files = `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) }
  spec.require_paths = ["lib"]
  spec.required_ruby_version = ">= 2.2.2"

  spec.add_dependency "activesupport"
  spec.add_development_dependency "bundler"
  spec.add_development_dependency "rake", "~> 10.0"
  spec.add_development_dependency "rspec", "3.5.0"
  spec.add_development_dependency "rubocop", "0.44.1"
end
```
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