[docs] Update the snippet to use latest Next.js template

[siriwatknp]

closes #45922

• Change the snippet from diff to tsx so that users can copy and paste to their project

---

• [ ] I have followed (at least) the PR section of the contributing guide.

[mui-bot]

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• docs/data/material/integrations/nextjs/nextjs.md

Bundle size report

Bundle	Parsed Size	Gzip Size
@mui/material	0B(0.00%)	0B(0.00%)
@mui/lab	0B(0.00%)	0B(0.00%)
@mui/system	0B(0.00%)	0B(0.00%)
@mui/utils	0B(0.00%)	0B(0.00%)

Details of bundle changes

Generated by :no_entry_sign: dangerJS against 4d54111248d2bf0b2bf6950cde893b73ce983605