[docs] QDBusUtil: remove documentation of bygone functions

The referenced QString overloads were removed when
6bbfae9457 ported from
QString/QStringRef overload sets to single QStringView functions.

Remove the docs.

Amends 6bbfae9457.

Pick-to: 6.7 6.6 6.5 6.2
Change-Id: I766ad104f83aa19d90eeefe5b67524184869640a
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

src/dbus/qdbusutil.cpp

@@ -309,13 +309,6 @@ namespace QDBusUtil
         return true;
     }
 
-    /*!
-        \internal
-        \fn bool isValidPartOfObjectPath(const QString &part)
-
-        \overload
-    */
-
     /*!
         \fn bool isValidInterfaceName(const QString &ifaceName)
         Returns \c true if this is \a ifaceName is a valid interface name.
@@ -375,12 +368,6 @@ namespace QDBusUtil
         return true;
     }
 
-    /*!
-        \fn bool isValidUniqueConnectionName(const QString &connName)
-
-        \overload
-    */
-
     /*!
         \fn bool isValidBusName(const QString &busName)
         Returns \c true if \a busName is a valid bus name.
@@ -443,12 +430,6 @@ namespace QDBusUtil
         return true;
     }
 
-    /*!
-        \fn bool isValidMemberName(const QString &memberName)
-
-        \overload
-    */
-
     /*!
         \fn bool isValidErrorName(const QString &errorName)
         Returns \c true if \a errorName is a valid error name. Valid error names are valid interface