flaky tst_QSpinBox::stepModifierPressAndHold() on Open SUSE

Integration is commonly failing with errors in this test, e.g.

• Open SUSE Jul/12: upShiftWithShiftKeyboardModifier, upNoWithMetaKeyboardModifier, downCtrlWithCtrlKeyboardModifier
• Open SUSE Jul/12: upShiftWithNoKeyboardModifier, downShiftWithAltKeyboardModifier
• Open SUSE Jul/13: upNoWithNoKeyboardModifier, upCtrlWithCtrlKeyboardModifier, upNoWithAltKeyboardModifier, upNoWithMetaKeyboardModifier, upCtrlWithShiftKeyboardModifier
• Open SUSE Jul/13: downCtrlWithMetaKeyboardModifier, downCtrlWithShiftKeyboardModifier, downCtrlWithAltKeyboardModifier
• Open SUSE Jul/13: upShiftWithCtrlKeyboardModifier, downShiftWithShiftKeyboardModifier
• Open SUSE Jul/16: upShiftWithShiftKeyboardModifier, downCtrlWithAltKeyboardModifier
• Open SUSE Jul/16: downShiftWithAltKeyboardModifier, upNoWithShiftKeyboardModifier
• Open SUSE Jul/16: downNoWithNoKeyboardModifier, downCtrlWithShiftKeyboardModifier, downNoWithCtrlKeyboardModifier, downShiftWithAltKeyboardModifier
• Open SUSE Jul/17: downCtrlWithShiftKeyboardModifier, downCtrlWithNoKeyboardModifier, downNoWithShiftKeyboardModifier, downNoWithCtrlKeyboardModifier, downShiftWithCtrlKeyboardModifier
• or see Grafana's statistics for this test.

I also note that tst_QDateTimeEdit::stepModifierKeys(upNoDayWithNoKeyboardModifier) fails in noticeably many (all?) of these, too – suggesting that step modifier gets upset somehow, possibly by something in Coin