Hyperlink DOIs to preferred resolver (see matplotlib#11470 & d6797ff) (matplotlib#13172)

Author: katrinleinweber

tutorials/colors/colormaps.py

@@ -422,5 +422,5 @@ def plot_color_gradients(cmap_category, cmap_list):
 # .. [bw] http://www.tannerhelland.com/3643/grayscale-image-algorithm-vb6/
 # .. [colorblindness] http://www.color-blindness.com/
 # .. [vischeck] http://www.vischeck.com/vischeck/
-# .. [IBM] https://dx.doi.org/10.1109/VISUAL.1995.480803
+# .. [IBM] https://doi.org/10.1109/VISUAL.1995.480803
 # .. [palettable] https://jiffyclub.github.io/palettable/