Doc Change: Change in shape for CIFAR Datasets (keras-team#11043)

* Doc Change: Change in shape for CIFAR Datasets

Both the CIFAR datasets have been updates now having the channel as the last dimension in the shape resulting in (num_samples, 32, 32, 3)

* Doc change added information on the shape of CIFAR datasets

The CIFAR datasets download in either channels_first or the channels_last format based on the backend setting.

Author: Sri Yogesh K

docs/templates/datasets.md

@@ -14,7 +14,7 @@ from keras.datasets import cifar10
 
 - __Returns:__
     - 2 tuples:
-        - __x_train, x_test__: uint8 array of RGB image data with shape (num_samples, 3, 32, 32).
+        - __x_train, x_test__: uint8 array of RGB image data with shape (num_samples, 3, 32, 32) or (num_samples, 32, 32, 3) based on the `image_data_format` backend setting of either `channels_first` or `channels_last` respectively.
         - __y_train, y_test__: uint8 array of category labels (integers in range 0-9) with shape (num_samples,).
 
 
@@ -34,7 +34,7 @@ from keras.datasets import cifar100
 
 - __Returns:__
     - 2 tuples:
-        - __x_train, x_test__: uint8 array of RGB image data with shape (num_samples, 3, 32, 32).
+        - __x_train, x_test__: uint8 array of RGB image data with shape (num_samples, 3, 32, 32) or (num_samples, 32, 32, 3) based on the `image_data_format` backend setting of either `channels_first` or `channels_last` respectively.
         - __y_train, y_test__: uint8 array of category labels with shape (num_samples,).
 
 - __Arguments:__
@@ -206,4 +206,4 @@ from keras.datasets import boston_housing
     - __test_split__: fraction of the data to reserve as test set.
 
 - __Returns:__
-    Tuple of Numpy arrays: `(x_train, y_train), (x_test, y_test)`.
+    Tuple of Numpy arrays: `(x_train, y_train), (x_test, y_test)`.