Mark scroll-behavior as flag-required in Safari (#7364)
Mark scroll-behavior as flag-required in Safari (#7364)

This change marks the CSS scroll-behavior property as requiring Safari
users to enable the “CSSOM View Smooth Scrolling” experimental feature.
mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data