Fix a false positive for Layout/RedundantLineBreak

[koic]

This PR fixes false positive for Layout/RedundantLineBreak to prevent the following infinite loop error:

$ echo 'x def self.y; z end' | be rubocop --stdin example.rb -a --only Layout/RedundantLineBreak,Style/SingleLineMethods
Inspecting 1 file
C

Offenses:

example.rb:1:1: C: [Corrected] Layout/RedundantLineBreak: Redundant line break detected.
x def self.y;  ...
^^^^^^^^^^^^^^
example.rb:1:3: C: [Corrected] Style/SingleLineMethods: Avoid single-line method definitions.
x def self.y; z end
  ^^^^^^^^^^^^^^^^^

0 files inspected, 2 offenses detected, 2 offenses corrected
Infinite loop detected in /Users/koic/src/github.com/rubocop/rubocop/example.rb and caused by Style/SingleLineMethods -> Layout/RedundantLineBreak
/Users/koic/src/github.com/rubocop/rubocop/lib/rubocop/runner.rb:332:in `check_for_infinite_loop'

---

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.