Doc: use standard wording in \brief commands

QDoc does some magic with the \class and \namespaces
and \brief commands, so the following wording must be used:
"The xxx class yyy ..."

Change-Id: Id231f30e8464898b776888d5423523de404aae34
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/libs/utils/detailswidget.cpp

@@ -41,7 +41,8 @@
 /*!
     \class Utils::DetailsWidget
 
-    \brief Widget a button to expand a 'Details' area.
+    \brief The DetailsWidget class implements a button to expand a \e Details
+    area.
 
     This widget is using a grid layout and places the items
     in the following way: