Merge pull request #6681 from afvincent/Typo_in_IdentityTransform_doc…

…string

Fix #6680 (minor typo in IdentityTransform docstring)

lib/matplotlib/transforms.py

@@ -2029,7 +2029,7 @@ def _get_is_separable(self):
 
 class IdentityTransform(Affine2DBase):
     """
-    A special class that does on thing, the identity transform, in a
+    A special class that does one thing, the identity transform, in a
     fast way.
     """
     _mtx = np.identity(3)