fix(vue): remove ssr.external config

[sapphi-red]

Description

IIUC since Vite 3 externalizes everything by default, this is not needed. Also this prevents #9117 to work well. So I think this should be removed.

fixes #9117

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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