Fix typo Ensomble -> Ensemble

Title says it all

Author: vicentealencar

autosklearn/estimators.py

@@ -339,7 +339,7 @@ def fit_ensemble(self, y, task=None, metric=None, precision='32',
             introduced in `Getting Most out of Ensemble Selection`.
 
         ensemble_size : int
-            Size of the ensemble built by `Ensomble Selection`.
+            Size of the ensemble built by `Ensemble Selection`.
 
         Returns
         -------