Fix copy-and-paste bug in QDTEP::getMaximum()
It had a copy of a line from getMinimum().
The results were predictably broken.
Pick-to: 5.15 6.1
Change-Id: I3582edb08696bec4311f43fc426f7e54dc069f53
Reviewed-by: Mårten Nordheim marten.nordheim@qt.io
(cherry picked from commit a15a3fef)