Clarify that there's no need for MSA when signing in with GitHub

[captainbrosset]

Rendered article section for review:

• Publish a Microsoft Edge extension by using a GitHub account - bottom of Intro section
  • Internal preview: https://review.learn.microsoft.com/microsoft-edge/extensions-chromium/publish/github?branch=pr-en-us-3058
  • Public preview: https://github.com/MicrosoftDocs/edge-developer/blob/main/microsoft-edge/extensions-chromium/publish/github.md
  • Before/Live: https://learn.microsoft.com/microsoft-edge/extensions-chromium/publish/github

This PR fixes #2716 by removing a confusing sentence about linking your github account to your MSA account. An MSA account is not needed in this scenario, so this sentence is confusing.

AB#48990073

[mikehoffms]

Approved PR, and asked SME to confirm that any linking of the accounts is done automatically in this scenario.

[learn-build-service-prod]

Learn Build status updates of commit bda1a37:

✅ Validation status: passed

File	Status	Preview URL	Details
microsoft-edge/extensions-chromium/publish/github.md	✅Succeeded	View

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