fix(components): [date-picker] slot compatible with Vue3.3.x

[FrontEndDog]

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Description

🤖 Generated by Copilot at 9592d64

Fix a bug with the date picker component when using v-if inside the cell slot. Filter out the virtual comment nodes from the cell render function in basic-cell-render.tsx.

Related Issue

Fixes #14342 .

Explanation of Changes

🤖 Generated by Copilot at 9592d64

• Fix a bug with the date picker when using v-if inside the cell slot by filtering out the virtual comment nodes (link)

[pull-request-triage]

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[github-actions]

[github-actions]

Hello @FrontEndDog, thank you for contributing to element-plus, please see our guideline to see how to make contribution

[FrontEndDog]

the type of virtual nodes in Vue3.2 is Symbol(Comment)，but in Vue3.3 is Symbol(v-cmt).It resulting in not displaying the date when writing empty nodes or explanator in the date-picker default slot.

[github-actions]

🧪 Playground Preview: https://element-plus.run/?pr=14354
Please comment the example via this playground if needed.

[btea]

Thanks!