[BUG] ImportError: cannot import name 'case_insensitive_dict' from 'azure.core.utils'

## Which example? Describe the issue

example: image_classification_keras_minist_convnet.ipynb
description: I am unable to run this example as `from azure.ai.ml import MLClient` in the first cell throws an import error.

## Additional context
I am running this example in the default Python 3.8 - AzureML kernel in Azure ML Studio. I recieve the same error if I follow the environment setup instructions on my local machine.

Just in case I've somehow screwed up my environment, here is a [pip freeze](https://gist.github.com/eschibli/12f7e26e95b87c584cc04efb4b712903)

Start with image_classification_keras_minist_convnet.ipynb and reproduce the ImportError from the first cell in the default Python 3.8 AzureML kernel and the local environment. Compare the pip freeze details with the environment setup instructions; done means the notebook imports MLClient successfully and can proceed past its first cell.

Written by the indexing model from the issue text.