LimitedIndexedTreeDataSet: fix yErrors

Fixes a small typo bug that would initialize tze yErrors with the
yValues instead of the supplied yValues.

Thanks to @zanzica for finding and repoting this.

Author: wirew0rm

chartfx-dataset/src/main/java/io/fair_acc/dataset/spi/LimitedIndexedTreeDataSet.java

@@ -447,7 +447,7 @@ public LimitedIndexedTreeDataSet set(final double[] xValues, final double[] yVal
                 final double x = xValues[i];
                 final double y = yValues[i];
                 final double dx = xErrors[i];
-                final double dy = yValues[i];
+                final double dy = yErrors[i];
                 getAxisDescription(DIM_X).add(x - dx);
                 getAxisDescription(DIM_X).add(x + dx);
                 getAxisDescription(DIM_Y).add(y - dy);