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/plugins/vcsbase/submitfieldwidget.cpp

@@ -53,7 +53,8 @@ static void inline setComboBlocked(QComboBox *cb, int index)
 
 /*!
     \class VcsBase::SubmitFieldWidget
-    \brief A widget for editing submit message fields like "reviewed-by:",
+    \brief The SubmitFieldWidget class is a widget for editing submit message
+    fields like "reviewed-by:",
     "signed-off-by:".
 
     It displays them in a vertical row of combo/line edit fields