fix errors in rubocop

[colby-swandale]

There is currently a couple of errors in rubocop that this PR is fixing:

❯ rubocop

Inspecting 97 files
...........................................................E.....................................

Offenses:

lib/rake/packagetask.rb:135:32: E: Lint/Syntax: unexpected token kDO_BLOCK
(Using Ruby 2.3 parser; configure using TargetRubyVersion parameter, under AllCops)
            chdir(package_dir) do
                               ^^
lib/rake/packagetask.rb:146:30: E: Lint/Syntax: unexpected token kDO_BLOCK
(Using Ruby 2.3 parser; configure using TargetRubyVersion parameter, under AllCops)
          chdir(package_dir) do
                             ^^
lib/rake/packagetask.rb:209:3: E: Lint/Syntax: unexpected token kEND
(Using Ruby 2.3 parser; configure using TargetRubyVersion parameter, under AllCops)
  end
  ^^^

97 files inspected, 3 offenses detected