QML: fix qml warning in NewTab.qml
QML: fix qml warning in NewTab.qml

Warning: "NewTab.qml:85: ReferenceError: Can't find variable:addbutton"
This is because addbutton object doesn't use any more. Just remove it.

Former-commit-id: e5145ad97d034c1bf98fe87563d0ac62a45c88ae
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser