fix: always add @sveltejs/kit to noExternal for ssr build

[dummdidumm]

fixes #9234

FYI @benmccann @Rich-Harris we always need @sveltejs/kit to be part of noExternal. Else the build output contains something like

import { redirect } from '@sveltejs/kit';

// some compiled code..
  redirect(307, '..');

while the output code also contains the SvelteKit server runtime, including their own definitions for Redirect etc classes, which means all instanceof checks fail.

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