Fix a typo

Author: tkanmae

doc/data-structures.rst

@@ -375,8 +375,8 @@ In addition to dictionary-like methods (described above), xarray has additional
 methods (like pandas) for transforming datasets into new objects.
 
 For removing variables, you can select and drop an explicit list of
-variables by using the by indexing with a list of names or using the
-:py:meth:`~xarray.Dataset.drop` methods to return a new ``Dataset``. These
+variables by indexing with a list of names or using the
+:py:meth:`~xray.Dataset.drop` methods to return a new ``Dataset``. These
 operations keep around coordinates:
 
 .. ipython:: python