DOC: Found a typo.

madphysicist · web-flow · commit 16ee11a200d3 · 2016-06-22T14:32:08.000-04:00
diff --git a/doc/users/annotations_guide.rst b/doc/users/annotations_guide.rst
@@ -399,7 +399,7 @@ callable object in following forms.::
 
               - *x0*, *y0*, *width*, *height* : location and size of the box
               - *mutation_size* : a reference scale for the mutation.
-              - *aspect_ratio* : aspect-ration for the mutation.
+              - *aspect_ratio* : aspect-ratio for the mutation.
             """
             path = ...
 	    return path
