WelcomeScreen: Improve vertical lines showing

Use lighter color of vertical line, from the overall look is more
consistent.
At least, the current design did not feel very comfortable.

Change-Id: I92d1513d475b1aadfc5ac58fc33f4ba84e6a8478
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@nokia.com>

share/qtcreator/welcomescreen/welcomescreen.qml

@@ -85,7 +85,7 @@ Rectangle {
         Rectangle {
             visible: root.width > 1042
             width: 2
-            color: "#919191"
+            color: "#cdcdcd"
             anchors.left: parent.left
             anchors.top: parent.top
             anchors.bottom: parent.bottom
@@ -94,7 +94,7 @@ Rectangle {
         Rectangle {
             visible: root.width > 1042
             width: 2
-            color: "#919191"
+            color: "#cdcdcd"
             anchors.right: parent.right
             anchors.top: parent.top
             anchors.bottom: parent.bottom