[Catalog] Remove the button scheme from the AppTheme. (#6510)
[Catalog] Remove the button scheme from the AppTheme. (#6510)

This property is no longer necessary now that we're able to theme buttons with the container scheme.

Related to https://github.com/material-components/material-components-ios/issues/6450

This change was extracted from https://github.com/material-components/material-components-ios/pull/6509

material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios