[Fix #10893] Fix an error when running rubocop without bundle exec

[koic]

Fixes #10893.

This PR fixes an error when running rubocop without bundle exec.

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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.

[koic]

@bbatsov This may be a critical issue for upgrades (1.34). It may be better to release a bugfix (1.34.1) release as soon as possible.
A separate reproduction test that excludes bundle exec may be possible, anyway I'm leaving a comment for now.

[dvandersluis]

There’s another ::Kernel.require a few lines below, does that need to be changed too?

rubocop/lib/rubocop/feature_loader.rb

Line 40 in 4b9f99b

::Kernel.require(namespaced_target)

[koic]

It concerns #10845 new feature. First of all, this PR focuses only on the compatibility part.

[bbatsov]

I'll cut a new release right away.

I hope @r7kamura will also find some time to look deeper into the cause of the problem.