Fixed the Value error in Example from activation.py

Passing Python list directly to the keras layer object in Example from activation.py is throwing Value error.  Fixed the error by passing tensor as a input. Here is the [gist](https://colab.sandbox.google.com/gist/LakshmiKalaKadali/caefd982bfff4ff6c4139784236c3a17/quickstart_colab.ipynb#scrollTo=F3hV2zfCb7Nu).

Thank You

keras/src/layers/activations/activation.py

@@ -15,10 +15,14 @@ class Activation(Layer):
     Example:
 
     >>> layer = keras.layers.Activation('relu')
-    >>> layer([-3.0, -1.0, 0.0, 2.0])
+    >>> input_data = np.array([-3.0, -1.0, 0.0, 2.0])  
+    >>> result = layer(input_data)  
+    >>> print(result)
     [0.0, 0.0, 0.0, 2.0]
     >>> layer = keras.layers.Activation(keras.activations.relu)
-    >>> layer([-3.0, -1.0, 0.0, 2.0])
+    >>> input_data = np.array([-3.0, -1.0, 0.0, 2.0])  
+    >>> result = layer(input_data) 
+    >>> print(result)
     [0.0, 0.0, 0.0, 2.0]
     """