Fix an error for InternalAffairs/NodeMatcherDirective

[koic]

This PR fixes the following error for InternalAffairs/NodeMatcherDirective.

% cat example.rb
def_node_matcher :foo?, format(PATTERN, type: 'const')

% bundle exec rubocop --only InternalAffairs/NodeMatcherDirective -d
(snip)

Inspecting 1 file
Scanning
/Users/koic/src/github.com/koic/rubocop-issues/ia_cop/example.rb
An error occurred while InternalAffairs/NodeMatcherDirective cop was
inspecting
/Users/koic/src/github.com/koic/rubocop-issues/ia_cop/example.rb:1:0.
undefined method `value' for s(:send, nil, :format,
  s(:const, nil, :PATTERN),
  s(:hash,
    s(:pair,
      s(:sym, :type),
      s(:str, "const")))):RuboCop::AST::SendNode
/Users/koic/src/github.com/rubocop/rubocop/lib/rubocop/cop/internal_affairs/node_matcher_directive.rb:100:in
`insert_directive'
/Users/koic/src/github.com/rubocop/rubocop/lib/rubocop/cop/internal_affairs/node_matcher_directive.rb:85:in
`block in register_offense'
(snip)

1 error occurred:
An error occurred while InternalAffairs/NodeMatcherDirective cop was
inspecting
/Users/koic/src/github.com/koic/rubocop-issues/ia_cop/example.rb:1:0.
Errors are usually caused by RuboCop bugs.
Please, report your problems to RuboCop's issue tracker.
https://github.com/rubocop/rubocop/issues

---

Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.

[dvandersluis]

No matter how many times I tried it of course I missed something 😅

thanks @koic!