[ui] Application: Fill window horizontally

The content of the application was filling the window's size vertically,
but not horizontally.

Author: cbentejac

meshroom/ui/qml/Application.qml

@@ -991,7 +991,7 @@ Page {
         MSplitView {
             id: topBottomSplit
             Layout.fillHeight: true
-            width: parent.width
+            Layout.fillWidth: true
 
             orientation: Qt.Vertical