[gtkmm-documentation] Fixed typo in string

[Daniel Mustieles GarcÃa <dmustieles src gnome org>]

commit 12dd1d01a6b427813a24cfdf9a8ff4b238406632
Author: Daniel Mustieles <daniel mustieles gmail com>
Date:   Fri Aug 10 10:29:43 2012 +0200

    Fixed typo in string

 docs/tutorial/C/gtkmm-tutorial-in.xml |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/docs/tutorial/C/gtkmm-tutorial-in.xml b/docs/tutorial/C/gtkmm-tutorial-in.xml
index c541a9b..a1cfec8 100644
--- a/docs/tutorial/C/gtkmm-tutorial-in.xml
+++ b/docs/tutorial/C/gtkmm-tutorial-in.xml
@@ -8043,7 +8043,7 @@ server.signal_something().connect(
 <sect1 id="chapter-custom-signals-example"><title>Example</title>
 
 <para>
-This is a full working example that defines and uses custom signal.
+This is a full working example that defines and uses custom signals.
 </para>
 
 <para><ulink url="&url_examples_base;signals/custom/">Source Code</ulink></para>