Notebookbar: correct initial icon size

Before this patch initial icon size
in the NotebookbarToolBox was determined
by Sidebar settings not Notebookbar

Change-Id: I66ac709c606ef60fb3505bbbe51dfebbcc81d20c
Reviewed-on: https://gerrit.libreoffice.org/35493
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Szymon Kłos <eszkadev@gmail.com>
diff --git a/sfx2/source/sidebar/SidebarToolBox.cxx b/sfx2/source/sidebar/SidebarToolBox.cxx
index 4874694..968366e 100644
--- a/sfx2/source/sidebar/SidebarToolBox.cxx
+++ b/sfx2/source/sidebar/SidebarToolBox.cxx
@@ -319,7 +319,10 @@ class NotebookbarToolBox : public SidebarToolBox
{
public:
    explicit NotebookbarToolBox(vcl::Window* pParentWindow)
        : SidebarToolBox(pParentWindow) {}
    : SidebarToolBox(pParentWindow)
    {
        SetToolboxButtonSize(GetDefaultButtonSize());
    }

    virtual ToolBoxButtonSize GetDefaultButtonSize() const override
    {