Convert tokenizer outputs for Keras in doc example (#20732)

* Convert tokenizer outputs for Keras in doc example

* Das deutsche Beispiel auch korrigieren

docs/source/de/training.mdx

@@ -185,6 +185,8 @@ from transformers import AutoTokenizer
 
 tokenizer = AutoTokenizer.from_pretrained("bert-base-cased")
 tokenized_data = tokenizer(dataset["text"], return_tensors="np", padding=True)
+# Tokenizer returns a BatchEncoding, but we convert that to a dict for Keras
+tokenized_data = dict(tokenized_data)
 
 labels = np.array(dataset["label"])  # Label is already an array of 0 and 1
 ```

docs/source/en/training.mdx

@@ -185,6 +185,8 @@ from transformers import AutoTokenizer
 
 tokenizer = AutoTokenizer.from_pretrained("bert-base-cased")
 tokenized_data = tokenizer(dataset["text"], return_tensors="np", padding=True)
+# Tokenizer returns a BatchEncoding, but we convert that to a dict for Keras
+tokenized_data = dict(tokenized_data)
 
 labels = np.array(dataset["label"])  # Label is already an array of 0 and 1
 ```