fix: ignore tsconfig target when bundling config

[sapphi-red]

Description

When target: es5 is set in tsconfig.json and vite.config.ts exists, Vite fails to start. This is because esbuild looks for that when bundling config.

Because we always ignore target in tsconfig.json and users won't expect target field to be respected for config loading, I think it is better to ignore target field here too.

reproduction: https://stackblitz.com/edit/vitejs-vite-h1gxde?file=vite.config.ts&terminal=dev

Additional context

related discussion: #3827

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What is the purpose of this pull request?

• [x] Bug fix
• [ ] New Feature
• [ ] Documentation update
• [ ] Other

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