doc: class QQuickCloseEvent added to module QtQuick

The wrong qdoc command had been used to add it to the
QML module QtQuick.Window. This caused a link to the
QML module to be not found by qdoc. The correct command
and C++ module name are now used.

Task-number: QTBUG-38529
Change-Id: I810f179d8f70dc8fb4d359ac3d4b192ef63ca429
Reviewed-by: Sze Howe Koh <szehowe.koh@gmail.com>