Doc: Replace type by class in QWERPHPRequest

qdoc has magic to remove the 'This XXX class' in the class overview,
but not type. See e.g.
http://doc-snapshots.qt.io/qt5-5.11/qtwebengine-modules.html



Change-Id: Idd38a860ae08c7199c322d16c3ccc737972131a0
Reviewed-by: Viktor Engelmann <viktor.engelmann@qt.io>