Fix typo in link to English Wikipedia page for Iris data set (#708)

Author: willschlitzer

examples/gallery/plot/scatter3d.py

@@ -4,7 +4,7 @@
 
 The :meth:`pygmt.Figure.plot3d` method can be used to plot symbols in 3D.
 In the example below, we show how the
-`Iris flower dataset <https://en.wikipedia.org/wiki/Iris_flower_data_set/>`__
+`Iris flower dataset <https://en.wikipedia.org/wiki/Iris_flower_data_set>`__
 can be visualized using a perspective 3-dimensional plot. The ``region``
 argument has to include the :math:`x`, :math:`y`, :math:`z` axis limits in the
 form of (xmin, xmax, ymin, ymax, zmin, zmax), which can be done automatically