Apply suggestions from code review

Co-authored-by: nabenabe0928 <47781922+nabenabe0928@users.noreply.github.com>

Author: ravinkohli

autoPyTorch/pipeline/components/preprocessing/tabular_preprocessing/variance_thresholding/VarianceThreshold.py

@@ -27,7 +27,7 @@ def fit(self, X: Dict[str, Any], y: Optional[Any] = None) -> 'VarianceThreshold'
 
     def transform(self, X: Dict[str, Any]) -> Dict[str, Any]:
         if self.preprocessor['numerical'] is None:
-            raise ValueError("cant call transform on {} without fitting first."
+            raise ValueError("cannot call transform on {} without fitting first."
                              .format(self.__class__.__name__))
         X.update({'variance_threshold': self.preprocessor})
         return X