gemspec: Explicitly empty the executables list

This gem exposes no executables.

Author: olleolleolle

forwardable.gemspec

@@ -21,6 +21,6 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = '>= 2.4.0'
   spec.files         = ["forwardable.gemspec", "lib/forwardable.rb", "lib/forwardable/impl.rb"]
   spec.bindir        = "exe"
-  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
+  spec.executables   = []
   spec.require_paths = ["lib"]
 end