Fixes #12899 - Move uninstall steps to top for brew

[sdwheeler]

PR Summary

Move uninstall steps to top for brew

• Fixes AB#565855
• Fixes powershell on macos using homebrew upgrade to 7.6 #12899

PR Checklist

• Descriptive Title: This PR's title is a synopsis of the changes it proposes.
• Summary: This PR's summary describes the scope and intent of the change.
• Contributor's Guide: I have read the contributor's guide.
• Style: This PR adheres to the style guide.

[learn-build-service-prod]

PoliCheck Scan Report

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[Copilot]

Pull request overview

Updates the macOS Homebrew installation guidance to better support users migrating from Homebrew cask-based installs to the current formula-based install flow.

Changes:

• Updates ms.date.
• Rewords the Homebrew intro text and link to Homebrew install instructions.
• Moves cask-uninstall steps ahead of the formula install command (within the IMPORTANT block).

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[Copilot]

The [!IMPORTANT] block contains blank blockquote lines (standalone >), which violates markdownlint MD028 (no-blanks-blockquote) and can cause inconsistent rendering. Remove the empty > lines and keep the content contiguous within the blockquote.

Suggested change

	>
	> If you previously installed PowerShell using the Homebrew cask, you must first uninstall the cask
	> before you can successfully install using the Homebrew formula. Use the following commands to
	> uninstall the cask:
	>
	> If you previously installed PowerShell using the Homebrew cask, you must first uninstall the cask
	> before you can successfully install using the Homebrew formula. Use the following commands to
	> uninstall the cask:

[learn-build-service-prod]

Learn Build status updates of commit 5ee32f7:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/docs-conceptual/install/alternate-install-methods.md	✅Succeeded	View (>=powershell-5.1)

For more details, please refer to the build report.