refactor: remove ternary operator because key is always true

[clarkdo]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
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Does this PR introduce a breaking change? (check one)

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• No

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• New/updated tests are included

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Other information:

When I read genOnce in vue-server-renderer/basic.js, I found that key will never be false here.

[Kingwl]

LGTM👍