Fix include value in Rails/AttributeDefaultBlockValue

[kkitadate]

Include value in AttributeDefaultBlockValue is incorrect, so i fix it.
(Although it has already been reported on #339 (comment))

---

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.
• If this is a new cop, consider making a corresponding update to the Rails Style Guide.

[koic]

Can you add a changelog entry?

• 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.

[kkitadate]

Can you add a changelog entry?

Thank you for your comment. It has completed.
(Should I rebase or squash? Please let me know if necessary)

[kkitadate]

• Squashed related commits together.

Due to the above, I will squash the commits.

[kkitadate]

It seems better to use Department/CopName when describing the cop name.

Thanks for the review. Fixed it.

[koic]

Thanks!