Migrating ViViT to Keras-3

[aditya02shah]

This PR migrates the ViViT example to Keras 3.0 as requested in keras-team/keras-cv#2211 and includes the following changes:

1. Replacing Tensorflow operations with their equivalent Keras ops in the preprocess function.

2. Reshaping of the tensor before saving to a GIF, to resolve the issue characterized by the error message TypeError: Cannot handle this data type: (1, 1, 1), |u1

[divyashreepathihalli]

@aditya02shah Thanks for the PR! If the example is using Tensorflow only for tf.data, this will be a keras 3 example. You can remove setting the backend line os.environ["KERAS_BACKEND"] = "tensorflow".
Also, Please generate the .ipynb and .md file. Here is how you do it - from keras-io/scripts/ run python autogen.py add_example ../examples/vision/python_file_name

[aditya02shah]

@divyashreepathihalli I have made the necessary changes and generated the .ipynb and .md files!