Update intelligent-query-processing-memory-grant-feedback.md

[sommarskog]

Topic said that persistence of memory-grant-feedback and percentile testing is currently not available in Azure Managed Instance. My testing indicates that it is, and I assume that the text I deleted was a leftover.

[learn-build-service-prod]

Learn Build status updates of commit 4c04f86:

⚠️ Validation status: warnings

File	Status	Preview URL	Details
docs/relational-databases/performance/intelligent-query-processing-memory-grant-feedback.md	⚠️Warning		Details

docs/relational-databases/performance/intelligent-query-processing-memory-grant-feedback.md

• Line 1, Column 1: [Warning: author-missing - See documentation] Missing required attribute: 'author'. Add the current author's GitHub ID.
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