Fix tst_QWebEngineView::crashTests test case

This test runs without crash, but fails because the expected
interval of the load progress is too narrow.

For example, the progress values in my case: 0 -> 10 -> 100

Change-Id: I0fd13d6badf717fc27e8d4219f39190db0090692
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>