[gtkmm-documentation] custom_container example: Remove use of set_redraw_on_allocate().

[Murray Cumming <murrayc src gnome org>]

commit 3aa586282331d7f95f25bfdd2230ab20079f77bb
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Aug 25 16:21:03 2017 +0200

    custom_container example: Remove use of set_redraw_on_allocate().

 .../book/custom/custom_container/mycontainer.cc    |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)
---
diff --git a/examples/book/custom/custom_container/mycontainer.cc 
b/examples/book/custom/custom_container/mycontainer.cc
index 7304ab9..a3f6ac1 100644
--- a/examples/book/custom/custom_container/mycontainer.cc
+++ b/examples/book/custom/custom_container/mycontainer.cc
@@ -22,7 +22,6 @@ MyContainer::MyContainer()
 : m_child_one(nullptr), m_child_two(nullptr)
 {
   set_has_window(false);
-  set_redraw_on_allocate(false);
 }
 
 MyContainer::~MyContainer()