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/linecolumnlabel.cpp

@@ -34,7 +34,8 @@
 /*!
     \class Utils::LineColumnLabel
 
-    \brief A label suitable for displaying cursor positions, etc. with a fixed
+    \brief The LineColumnLabel class is a label suitable for displaying cursor
+    positions, and so on, with a fixed
     width derived from a sample text.
 */