fix(ssr): properly resolve suspense in teleport

[edison1105]

close #6207

the root cause is that targetBuffer may be a two-dimensional array.

https://github.com/vuejs/core/blob/0a8be4537af4535fbbde4161b8aff0f952ba0912/packages/server-renderer/src/helpers/ssrRenderTeleport.ts#L28-L36

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Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	89.5 kB	34.1 kB	30.7 kB
vue.global.prod.js	147 kB	53.3 kB	47.6 kB

Usages

Name	Size	Gzip	Brotli
createApp	49.8 kB	19.5 kB	17.8 kB
createSSRApp	53.1 kB	20.8 kB	19 kB
defineCustomElement	52.1 kB	20.2 kB	18.5 kB
overall	63.3 kB	24.4 kB	22.2 kB