Require RuboCop 0.90 or higher due to use RESTRICT_ON_SEND

[koic]

Follow rubocop/rubocop#8365

This PR uses RESTRICT_ON_SEND to restrict callbacks on_send to specific method names only.
RESTRICT_ON_SEND has been introduced since RuboCop 0.90.

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• Commit message starts with [Fix #issue-number] (if the related issue exists).
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• Added tests.
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