Fix rubocop style issues in yarn and spring.rb templates"

railties/lib/rails/generators/rails/app/templates/bin/yarn

 VENDOR_PATH = File.expand_path('..', __dir__)
 Dir.chdir(VENDOR_PATH) do
   begin
-    exec "yarnpkg #{ARGV.join(" ")}"
+    exec "yarnpkg #{ARGV.join(' ')}"
   rescue Errno::ENOENT
     $stderr.puts "Yarn executable was not detected in the system."
     $stderr.puts "Download Yarn at https://yarnpkg.com/en/docs/install"

railties/lib/rails/generators/rails/app/templates/config/spring.rb

-%w(
+%w[
   .ruby-version
   .rbenv-vars
   tmp/restart.txt
   tmp/caching-dev.txt
-).each { |path| Spring.watch(path) }
+].each { |path| Spring.watch(path) }