[gtkmm] Builder: Properly qualify static member function

[Daniel Boles <dboles src gnome org>]

commit 81456638be9ecd559c944a9185eb036f63ca5881
Author: Daniel Boles <dboles src gnome org>
Date:   Mon Dec 17 00:00:12 2018 +0000

    Builder: Properly qualify static member function
    
    We don't have UFCS, and ADL only works on namespaces, so we can't eschew
    the class name (unless inside Builder itself, which doc examples aren't)

 gtk/src/builder.hg | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/src/builder.hg b/gtk/src/builder.hg
index 6c202ea9..889d3e4b 100644
--- a/gtk/src/builder.hg
+++ b/gtk/src/builder.hg
@@ -500,8 +500,8 @@ public:
    * @code
    * MyDerivedDialog* pDialog1 = nullptr;
    * MyDerivedDialog* pDialog2 = nullptr;
-   * get_widget_derived(refBuilder, "mydialog1", pDialog1);
-   * get_widget_derived(refBuilder, "mydialog2", pDialog2, "A storm is imminent!", true);
+   * Gtk::Builder::get_widget_derived(refBuilder, "mydialog1", pDialog1);
+   * Gtk::Builder::get_widget_derived(refBuilder, "mydialog2", pDialog2, "A storm is imminent!", true);
    * @endcode
    *
    * @note