Axes -> axis in whatsnew change

Morgan243 · Morgan243 · commit 6510d2692802 · 2017-07-15T16:08:13.000-04:00
diff --git a/doc/source/whatsnew/v0.21.0.txt b/doc/source/whatsnew/v0.21.0.txt
@@ -166,7 +166,7 @@ I/O
 
 Plotting
 ^^^^^^^^
-- Bug in plotting methods using ``secondary_y`` and ``fontsize`` not setting secondary axes font size (:issue:`12565`)
+- Bug in plotting methods using ``secondary_y`` and ``fontsize`` not setting secondary axis font size (:issue:`12565`)
 
 
 Groupby/Resample/Rolling
