Direct2D QPA: Add missing break statement

Change-Id: Ib40daa1ba56cce423b29ac8f1ab50e4638980728
Reviewed-by: Risto Avila <risto.avila@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.cpp

@@ -469,6 +469,7 @@ public:
             break;
         case Qt::RoundCap:
             props.startCap = props.endCap = props.dashCap = D2D1_CAP_STYLE_ROUND;
+            break;
         case Qt::FlatCap:
         default:
             props.startCap = props.endCap = props.dashCap = D2D1_CAP_STYLE_FLAT;