[gtkmm-documentation] Update calls to Gtk::Snapshot::append_cairo()

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 970f0e57e96fcd23d1a37c25b7a31bac79f1393e
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Thu May 24 15:05:21 2018 +0200

    Update calls to Gtk::Snapshot::append_cairo()
    
    The 'name' parameter has been dropped from append_cairo().

 examples/book/custom/custom_widget/mywidget.cc           | 2 +-
 examples/others/cellrenderercustom/cellrenderertoggle.cc | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/examples/book/custom/custom_widget/mywidget.cc b/examples/book/custom/custom_widget/mywidget.cc
index 0510424..64f1582 100644
--- a/examples/book/custom/custom_widget/mywidget.cc
+++ b/examples/book/custom/custom_widget/mywidget.cc
@@ -172,7 +172,7 @@ void MyWidget::snapshot_vfunc(const Glib::RefPtr<Gtk::Snapshot>& snapshot)
   auto refStyleContext = get_style_context();
 
   // Create a cairo context to draw on.
-  auto cr = snapshot->append_cairo(rect, "MyCairoNode");
+  auto cr = snapshot->append_cairo(rect);
 
   // paint the background
   refStyleContext->render_background(cr,
diff --git a/examples/others/cellrenderercustom/cellrenderertoggle.cc 
b/examples/others/cellrenderercustom/cellrenderertoggle.cc
index 697c86a..e3b049e 100644
--- a/examples/others/cellrenderercustom/cellrenderertoggle.cc
+++ b/examples/others/cellrenderercustom/cellrenderertoggle.cc
@@ -204,7 +204,7 @@ void MyCellRendererToggle::snapshot_vfunc(const Glib::RefPtr<Gtk::Snapshot>& sna
   style_context->set_state(state);
 
   // Create a cairo context to draw on.
-  auto cr = snapshot->append_cairo(cell_area, "MyCairoNode");
+  auto cr = snapshot->append_cairo(cell_area);
 
   if (property_radio_)
   {