Fix video embed for Powertoys intro page

[jongalloway]

This video embed isn't working, docs indicate these should be prefaced by > to work.

[prmerger-automator[bot]]

@jongalloway : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[learn-build-service-prod[bot]]

Learn Build status updates of commit 15ca3f5:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
hub/powertoys/index.md	:white_check_mark:Succeeded

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