Fix false positives for Lint/LiteralAssignmentInCondition

[koic]

This PR fixes the following false positive for Lint/LiteralAssignmentInCondition when a collection lireal contains non-literal elements:

$ echo 'x = 1; if test = [42, x]; end' | be rubocop --stdin test.rb --only Lint/LiteralAssignmentInCondition
Inspecting 1 file
W

Offenses:

test.rb:1:16: W: Lint/LiteralAssignmentInCondition: Don't use literal assignment = [42, x] in conditional,
should be == or non-literal operand.
x = 1; if test = [42, x]; end
               ^^^^^^^^^

1 file inspected, 1 offense detected

In cases where non-literal elements are included in the collection, no warning will be displayed.

$ ruby -we 'x = 1; if test = [42, x]; end'

---

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• 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).
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• 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.