Cocoa: fix bug when left mouse button release event delivered as right

The regression was introduced during refactoring by 820e69d6c and the
initial change that added this logic is adc3ef97d.

This condition had become redundant and wrong after refactoring because
m_sendUpAsRightButton flag is set in the proper way in
QNSView::mouseDown() which later calls QNSView::handleMouseEvent()
anyway.

Task-number: QTBUG-58219
Change-Id: I1951cf4067af6f0c1837c1c15b8a09dfe7939493
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Pavol Markovic

src/plugins/platforms/cocoa/qnsview.mm

@@ -853,9 +853,6 @@ static bool _q_dontOverrideCtrlLMB = false;
     if (masked)
         return false;
 
-    if (button == Qt::RightButton)
-        m_sendUpAsRightButton = true;
-
     m_buttons |= button;
 
     [self handleMouseEvent:theEvent];