[Fix #7957] Fix Style/IfUnlessModifier to remain multiline if code after end keyword makes it too long

[dmytro-savochkin]

Fixes #7957.

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• 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.
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[bbatsov]

I really hope that no one actually writes such code. 😆

[bbatsov]

Looks good. Thanks!