Remove the Qt 5 todo about empty string lists in QSettings

There's no need to change behaviour now. The current marker (@Invalid())
returns an empty string list, as opposed to a list with one item.
Changing it would break compatibility unpredictably with Qt 4.

So I choose not to change QSettings. Let it be "Done".

Task-number: QTBUG-25110
Change-Id: Id1f353dfed800005d927183da237f3f8357c496d
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
Reviewed-by: Jason McDonald <jason.mcdonald@nokia.com>

src/corelib/io/qsettings.cpp

@@ -775,8 +775,6 @@ void QSettingsPrivate::iniEscapedStringList(const QStringList &strs, QByteArray
             with Qt 4.0. @Invalid() stands for QVariant(), and
             QVariant().toStringList() returns an empty QStringList,
             so we're in good shape.
-
-            ### Qt 5: Use a nicer syntax, e.g. @List, for variant lists
         */
         result += "@Invalid()";
     } else {