[libhandy] doc: Mention the renamed HdyClamp style classes

[Alexander Mikhaylenko <alexm src gnome org>]

commit 27362d512bf47124df2f44d92bf6185191d385f9
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Wed Jun 17 18:50:55 2020 +0200

    doc: Mention the renamed HdyClamp style classes

 doc/hdy-migrating-0-0-to-1.xml | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/doc/hdy-migrating-0-0-to-1.xml b/doc/hdy-migrating-0-0-to-1.xml
index 9c239058..99a54afd 100644
--- a/doc/hdy-migrating-0-0-to-1.xml
+++ b/doc/hdy-migrating-0-0-to-1.xml
@@ -111,6 +111,8 @@
         Its “maximum-width” and “linear-growth-width” properties have been
         renamed #HdyClamp:maximum-size and #HdyClamp:tightening-threshold
         respectively to better reflect their role.
+        It won't set the .narrow, .medium and .wide style classes depending on
+        its size, but the .small, .medium and .large ones instead.
       </para>
     </refsect3>