refactor(date-picker): optimize code

[chouchouji]

Checklist

List of tasks you have already done and plan to do.

• [ ] Fix linting errors
• [ ] Tests have been added / updated (or snapshots)

Change information

Describe your modifications here.

Issues

The issues you want to close, formatted as close #1.

Related Links

Links related to this pr.

[vercel[bot]]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
varlet	✅ Ready (Inspect)	Visit Preview		Apr 9, 2024 9:22am
varlet-ui-playground	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 9, 2024 9:22am

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 90.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 92.77%. Comparing base (250be9b) to head (aea892a). Report is 1 commits behind head on dev.

Files	Patch %	Lines
...arlet-ui/src/date-picker/src/year-picker-panel.vue	90.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #1580 +/- ## ========================================== - Coverage 92.78% 92.77% -0.01% ========================================== Files 306 306 Lines 7176 7227 +51 Branches 1788 1810 +22 ========================================== + Hits 6658 6705 +47 - Misses 452 456 +4 Partials 66 66 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.