DOC: Fix misspelling in get_dummies docstring (pandas-dev#26207)

Author: max-kov

pandas/core/reshape/reshape.py

@@ -718,7 +718,7 @@ def get_dummies(data, prefix=None, prefix_sep='_', dummy_na=False,
         If `columns` is None then all the columns with
         `object` or `category` dtype will be converted.
     sparse : bool, default False
-        Whether the dummy-encoded columns should be be backed by
+        Whether the dummy-encoded columns should be backed by
         a :class:`SparseArray` (True) or a regular NumPy array (False).
     drop_first : bool, default False
         Whether to get k-1 dummies out of k categorical levels by removing the