[gnomemm-website] Comment out the paragraph saying that gtkmm is updated regularly

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 8ae44c71081dcc85dbb4e418db7a87c79eb6daea
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Fri Feb 4 17:04:27 2022 +0100

    Comment out the paragraph saying that gtkmm is updated regularly
    
    It's not true at the moment. See e.g. issue gtkmm#110.

 docs/C/main.xml | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/docs/C/main.xml b/docs/C/main.xml
index b9eb896..1fbf3bc 100644
--- a/docs/C/main.xml
+++ b/docs/C/main.xml
@@ -21,11 +21,14 @@
    &gtkmm; is free software distributed under the GNU Lesser General
     Public License (<link xlink:href="license.html">LGPL</link>).
   </para>
+  <!-- 2022-02-04: Gtkmm is not released "on a predictable schedule" now.
+       Hopefully it will in the future. Keep this paragraph as a comment.
       <para>
    &gtkmm; follows the official <link xlink:href="https://www.gnome.org/start/unstable/";> GNOME Platform 
Bindings release schedule</link>. This guarantees
    API/ABI-stability and new releases on a predictable schedule,
    delivering C++ API for the underlying GTK and GNOME APIs as soon as possible.
   </para>
+  -->
     </note>
 
     <section>