Add license disclaimer

[JavierMatosD]

Follow up after https://github.com/microsoft/vcpkg-docs/pull/351

[prmerger-automator[bot]]

@JavierMatosD : 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 11c7115:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
vcpkg/maintainers/functions/vcpkg_install_copyright.md	:white_check_mark:Succeeded	View

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