linear_learner_mnist_with_file_system_data_source.ipynb needs SDKv2 Upgrade

https://github.com/awslabs/amazon-sagemaker-examples/blob/master/introduction_to_amazon_algorithms/linear_learner_mnist/linear_learner_mnist_with_file_system_data_source.ipynb

It upgrades to v2, then fails. Needs the pip install line to be removed or updated/pinned to v1.

Open introduction_to_amazon_algorithms/linear_learner_mnist/linear_learner_mnist_with_file_system_data_source.ipynb and inspect the pip install line. Run the notebook after the SDKv2 upgrade, then verify that removing or adjusting the install line resolves the failure and the example completes successfully.

Written by the indexing model from the issue text.