Remove CopySrcInsteadOfClone override from Build.props

[MichaelSimons]

aspire/eng/Build.props

Line 12 in 3d82b0f

<!-- When building from source, we want to use the live repo contents as opposed to cloning the repo. -->

This logic is no longer need with Arcade 9 as this is now the default/only behavior. After Aspire updates to Arcade 9, this cleanup work should be completed.