QEasingCurve: remove a default case label

A default: case label turns off compiler warnings for missing
enumeration values, which we'd like to have, so remove it.

Change-Id: I96247a7fc46e91a29591a907e52841a90df62f10
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/tools/qtimeline.cpp

@@ -529,7 +529,6 @@ QTimeLine::CurveShape QTimeLine::curveShape() const
 void QTimeLine::setCurveShape(CurveShape shape)
 {
     switch (shape) {
-    default:
     case EaseInOutCurve:
         setEasingCurve(QEasingCurve(QEasingCurve::InOutSine));
         break;