PdfMultiPageView: pinching on a link can jump rather than pinching

tst_MultiPageView::pinchDragPinch was pinching where one touchpoint happens to fall on a PdfLinkDelegate, and I forgot if I intended or noticed that, until it failed. https://codereview.qt-project.org/c/qt/qtdeclarative/+/557654 makes the TapHandler in PdfLinkDelegate actually emit the tapped signal when it's deactivated, even though one of the grab transitions is CancelGrabPassive. Probably it should not do that... if we can figure out the logic for why it shouldn't. If a person is trying to pinch, we can't expect that both points are pressed at the same time; so if one point is pressed, and then another, either of them can land on a PdfLinkDelegate. And then it's disorienting if the view jumps to a completely different location while trying to pinch.

We just avoid that for now, by adjusting the test to pinch at a different location: https://codereview.qt-project.org/c/qt/qtwebengine/+/633394