DOC: Fix the bars having numeric value of cm but labeled as inches

This is admittedly more of a band-aid than a proper fix, but at least
make the generated figure correct.

The underlying problem is the more fundemental one of inconsistent units
behavior in which some artists can be re-united after plotting (e.g.
Line2D), while many others (e.g. Collections) cannot.

Thus, until that is addressed (which is one of the goals of the
data-prototype work), simply setting units early is as good as we can
do.

Closes matplotlib#5051

Author: ksunden

galleries/examples/units/bar_unit_demo.py

@@ -22,6 +22,7 @@
 tea_std = [2*cm, 1*cm, 1*cm, 4*cm, 2*cm]
 
 fig, ax = plt.subplots()
+ax.yaxis.set_units(inch)
 
 ind = np.arange(N)    # the x locations for the groups
 width = 0.35         # the width of the bars
@@ -36,7 +37,6 @@
 ax.set_xticks(ind + width / 2, labels=['G1', 'G2', 'G3', 'G4', 'G5'])
 
 ax.legend()
-ax.yaxis.set_units(inch)
 ax.autoscale_view()
 
 plt.show()