[atkmm] Update atk_docs_override.xml

[Kjell Ahlstedt <kjellahl src gnome org>]

commit acbbf630844015cbbad84c81eb3ec9447073aeaf
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Wed Aug 25 08:51:14 2021 +0200

    Update atk_docs_override.xml

 atk/src/atk_docs_override.xml | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/atk/src/atk_docs_override.xml b/atk/src/atk_docs_override.xml
index ead0f9f..6b38568 100644
--- a/atk/src/atk_docs_override.xml
+++ b/atk/src/atk_docs_override.xml
@@ -1,5 +1,7 @@
 <root>
 <substitute_type_name from="GObject" to="Glib::Object" />
+<substitute_type_name from="GIOChannel" to="Glib::IOChannel" />
+
 <substitute_enumerator_name from_prefix="ATK_RELATION_" to_prefix="Atk::Relation::Type::" />
 <substitute_enumerator_name from="ATK_RELATION_NULL" to="Atk::Relation::Type::NONE" />
 <substitute_enumerator_name from_prefix="ATK_ROLE_" to_prefix="Atk::Role::" />