docs(type-providers): replace FastifyLoggerInstance with FastifyBaseLogger

[samialdury]

Type FastifyLoggerInstance has been marked as deprecated in favor of FastifyBaseLogger.

fastify/types/logger.d.ts

Lines 27 to 30 in 450416e

	/**
	* @deprecated Use FastifyBaseLogger instead
	*/
	export type FastifyLoggerInstance = FastifyBaseLogger

This commit replaces it with the correct type in the example snippet.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[github-actions]

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