Align Line on TabBar on bottom of scrollView on X

[MattKiazyk]

Using the TabsController Sample, if you add a line with and alignment of bottom, since the changes on Material 2.12.10 on iPhoneX, the line does not show up.

class AppTabsController: TabsController {
    open override func prepare() {
        super.prepare()
                tabBarAlignment = .bottom
                tabBar.tabBarStyle = .auto
                tabBar.dividerColor = nil
                tabBar.lineHeight = 5.0
                tabBar.lineAlignment = .bottom
                tabBar.lineColor = UIColor.blue
                tabBar.backgroundColor = Color.white
    }
}

If you look at the debugger the line is actually shown in the unsafe area at the bottom of X

This PR fixes the issue by putting line at the bottom of the scrollView, not the bounds of the TabBar.

[daniel-jonathan]

You can find this merge in Material 2.12.12. Thank you!