Update axis_artist.py

Issue - The axisartist.axis_artist docs page has a typo: ax.axis["bottom"].major_ticks.set_ticks_out(True) should be ax.axis["bottom"].major_ticks.set_tick_out(True) (remove 's' after 'tick' in 'set_tick_out')
Fixed it by removing the s

Author: aflah02

lib/mpl_toolkits/axisartist/axis_artist.py

@@ -73,7 +73,7 @@
 Ticks are by default direct opposite side of the ticklabels. To make ticks to
 the same side of the ticklabels, ::
 
-  ax.axis["bottom"].major_ticks.set_ticks_out(True)
+  ax.axis["bottom"].major_ticks.set_tick_out(True)
 
 The following attributes can be customized (use the ``set_xxx`` methods):