Set position and width of card in details page

This means that the card itself shouldn't specify a width. It should get a width from how it's used.

Contributes to issue CURA-8565.

plugins/Marketplace/resources/qml/Packages.qml

@@ -77,6 +77,7 @@ ListView
         PackageCard
         {
             packageData: model.package
+            width: parent.width - UM.Theme.getSize("default_margin").width - UM.Theme.getSize("narrow_margin").width
         }
     }