Doc: Add documentation for parameters to fix QDoc errors

In QWebEngineRegisterProtocolHandlerPermissionRequest::operator==(),
QWebEngineRegisterProtocolHandlerPermissionRequest::operator!=(),
QWebEngineQuotaPermissionRequest::operator==(), and
QWebEngineQuotaPermissionRequest::operator!=().

Change-Id: I0eaf1136b67396b678cc743dffd1e35f585f0c0c
Reviewed-by: Jüri Valdmann <juri.valdmann@qt.io>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>