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/git/branchadddialog.cpp

@@ -37,7 +37,8 @@ namespace Git {
 namespace Internal {
 
 /*!
- * \brief Validates the corresponding string as a valid git branch name
+ * \brief The BranchNameValidator class validates the corresponding string as
+ * a valid Git branch name.
  *
  * The class does this by a couple of rules that are applied on the string.
  *