Add an else condition to correct `StubbedMock` behavior

[corsonknowles]

Fix edge case for StubbedMock where it could return a blank suggestion for unhandled Expectation types.

Completes branch coverage for this file.

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Before submitting the PR make sure the following are checked:

• [x] Feature branch is up-to-date with master (if not - rebase it).
• [x] Squashed related commits together.
• [x] Added tests.
• [ ] Updated documentation.
• [ ] Added an entry to the CHANGELOG.md if the new code introduces user-observable changes.
• [x] The build (bundle exec rake) passes (be sure to run this locally, since it may produce updated documentation that you will need to commit).

If you have created a new cop:

• [ ] Added the new cop to config/default.yml.
• [ ] The cop is configured as Enabled: pending in config/default.yml.
• [ ] The cop is configured as Enabled: true in .rubocop.yml.
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• [ ] The tests assert both that bad code is reported and that good code is not reported.
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If you have modified an existing cop's configuration options:

• [ ] Set VersionChanged: "<<next>>" in config/default.yml.

[corsonknowles]

Hmm, I think this spec passes both before and after the change, so there is some issue here:

  it 'flags `are_expected`' do
    expect_offense(<<~RUBY)
      are_expected.to receive(:bar).and_return(:baz)
      ^^^^^^^^^^^^ Prefer `` over `are_expected` when configuring a response.
    RUBY
  end

[corsonknowles]

Okay, I pushed up a real change -- now it only flags on the methods it can correct.

Thoughts?

[corsonknowles]

Okay, how's this approach?

[pirj]

Perfect, thank you, @corsonknowles !