Remove repeated word from docstring [ci skip] (scikit-learn#13141)

Author: chkoar

sklearn/impute.py

@@ -408,7 +408,7 @@ def transform(self, X):
 class MissingIndicator(BaseEstimator, TransformerMixin):
     """Binary indicators for missing values.
 
-    Note that this component typically should not not be used in a vanilla
+    Note that this component typically should not be used in a vanilla
     :class:`Pipeline` consisting of transformers and a classifier, but rather
     could be added using a :class:`FeatureUnion` or :class:`ColumnTransformer`.