[rubygems/rubygems] Simplify the gem package file filter in the gemspec template

The regular expression is difficult to understand at a glance.
Let's replace it with a much simpler string comparison.

https://github.com/rubygems/rubygems/commit/a3745aa03f

lib/bundler/templates/newgem/newgem.gemspec.tt

@@ -29,7 +29,7 @@ Gem::Specification.new do |spec|
   # The `git ls-files -z` loads the files in the RubyGem that have been added into git.
   spec.files = Dir.chdir(__dir__) do
     `git ls-files -z`.split("\x0").reject do |f|
-      (File.expand_path(f) == __FILE__) || f.match(%r{\A(?:(?:bin|test|spec|features)/|\.(?:git|circleci)|appveyor)})
+      (File.expand_path(f) == __FILE__) || f.start_with?(*%w[bin test spec features .git .circleci appveyor])
     end
   end
   spec.bindir = "exe"