[gtkmm-documentation] Fix a doubly-defined section id

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 2dfeedc66d5c4b7db742207d3b812b8d5aed204f
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Mon Feb 19 13:39:29 2018 +0100

    Fix a doubly-defined section id
    
    The previous commit introduced a section id, which was already used.

 docs/tutorial/C/index-in.docbook |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/docs/tutorial/C/index-in.docbook b/docs/tutorial/C/index-in.docbook
index d5d93e5..dc2548f 100644
--- a/docs/tutorial/C/index-in.docbook
+++ b/docs/tutorial/C/index-in.docbook
@@ -5560,7 +5560,7 @@ if (info)
       <classname>FileChooserDialog</classname>, but you can embed it into your
       user interface if you want to.
     </para>
-    <sect2 id="filechooserdialog-example">
+    <sect2 id="recentfiles-example">
       <title>Simple FileChooserDialog example</title>
       <para>
         Shown below is a simple example of how to use the