Fix typo

[changeworld]

Github -> GitHub

[learn-build-service-prod]

Learn Build status updates of commit 84dbf66:

⚠️ Validation status: warnings

File	Status	Preview URL	Details
docs-ref-services/latest/core-index.md	⚠️Warning	View (azure-node-latest)	Details

docs-ref-services/latest/core-index.md

• Line 0, Column 0: [Warning: h1-missing - See documentation] H1 is required. Use a single hash (#) followed by a space to create your top-level heading.
• Line 1, Column 1: [Warning: title-missing - See documentation] Missing required attribute: 'title'. Add a title string to show in search engine results.
• Line 1, Column 1: [Warning: ms-prod-or-service-missing - See documentation] One of the following attributes is required: 'ms.prod', 'ms.service'. Use ms.prod for on-premise products, or ms.service for cloud services.
• Line 1, Column 1: [Suggestion: description-missing - See documentation] Missing required attribute: 'description'.
• Line 1, Column 1: [Suggestion: ms-topic-missing - See documentation] Missing required attribute: 'ms.topic'.

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