get_by_name() Code snippet Missing "workspace" definition

As the title suggests the code snippet for `get_by_name()` does not explicitly mention that defining a workspace is required to use the function.

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* ID: 1b905f15-6470-b8cf-0963-efb5c16a848d
* Version Independent ID: 02bcf9a3-057d-b4e4-3f6d-acbe8a689ba8
* Content: [azureml.core.dataset.Dataset class - Azure Machine Learning Python](https://learn.microsoft.com/en-us/python/api/azureml-core/azureml.core.dataset.dataset?view=azure-ml-py#get-by-name-workspace--name--version--latest--)
* Content Source: [AzureML-Docset/stable/docs-ref-autogen/azureml-core/azureml.core.dataset.Dataset.yml](https://github.com/MicrosoftDocs/MachineLearning-Python-pr/blob/live/AzureML-Docset/stable/docs-ref-autogen/azureml-core/azureml.core.dataset.Dataset.yml)
* Service: **machine-learning**
* Sub-service: **core**
* GitHub Login: @DebFro
* Microsoft Alias: **debfro**