Remove unnecessary horizontalCenter anchor

Left and right anchors can't work at the same time with the horizontalCenter. In this case it
makes more sence to remove the horizontalCenter, since the left and right ones also define the
width of the rectangle.

CURA-8014

resources/qml/WelcomePages/WhatsNewContent.qml

@@ -47,7 +47,6 @@ Item
             bottom: whatsNewDots.top
             left: parent.left
             right: parent.right
-            horizontalCenter: parent.horizontalCenter
             margins: UM.Theme.getSize("default_margin").width * 2
         }