[components-webview] Respect component height. Fixes JB#57689

Ensures that the Gecko rendering height is the same as the component
height, rather than being fixed to the height of the screen.

This prevents content being lost from the bottom of the WebView in case
the height is shorter than the screen height.

import/webview/WebView.qml

@@ -66,7 +66,7 @@ RawWebView {
     _acceptTouchEvents: !textSelectionActive
 
     viewportHeight: webViewPage
-            ? ((webViewPage.orientation & Orientation.PortraitMask) ? Screen.height : Screen.width)
+            ? ((webViewPage.orientation & Orientation.PortraitMask) ? height : width)
             : undefined
 
     orientation: {