Skip linearGradientSymmetry test on QWS.

QWS defines GRADIENT_STOPTABLE_SIZE to be 256, which is not enough
resolution for this test to pass.

Reviewed-by: Eskil Abrahamsen Blomfeldt
(cherry picked from commit 0201d5f5a8c95bd4f6b94726ed0db2b83cd3efc7)

tests/auto/qpainter/tst_qpainter.cpp

@@ -4016,6 +4016,9 @@ void tst_QPainter::linearGradientSymmetry_data()
 
 void tst_QPainter::linearGradientSymmetry()
 {
+#ifdef Q_WS_QWS
+    QSKIP("QWS has limited resolution in the gradient color table", SkipAll);
+#else
     QFETCH(QGradientStops, stops);
 
     QImage a(64, 8, QImage::Format_ARGB32_Premultiplied);
@@ -4037,6 +4040,7 @@ void tst_QPainter::linearGradientSymmetry()
 
     b = b.mirrored(true);
     QCOMPARE(a, b);
+#endif
 }
 
 void tst_QPainter::gradientInterpolation()