Backport PR matplotlib#31580: DOC: added unregister to colormap guide

Author: QuLogic

galleries/users_explain/colors/colormap-manipulation.py

@@ -299,6 +299,11 @@ def plot_linearmap(cdict):
 
 plt.show()
 
+# %%
+# Colormaps added to the registry can also be deregistered:
+
+mpl.colormaps.unregister(my_cmap.name)
+
 # %%
 #
 # .. admonition:: References