Remove unnecessary checkout: none that causes conflicts with sparse checkout declarations

[benbp]

This was causing checkout: none to appear twice in release pipeline yaml, which caused someone to add SkipDefaultCheckout to the sparse checkout parameters in order to avoid the conflict. However, this meant that we were then doing full clones in some places.

[weshaggard]

I assume we are already fixed the consumers so they don't end up with full clones.

[azure-sdk]

The following pipelines have been queued for testing:
java - template
java - template - tests
js - template
net - template
net - template - tests
python - template
python - template - tests
You can sign off on the approval gate to test the release stage of each pipeline.
See eng/common workflow

[benbp]

I assume we are already fixed the consumers so they don't end up with full clones.

@weshaggard yeah that was actually how I found this problematic line. I fixed the consumers, which worked for all my test cases, but it broke the spring-experimental CI/release pipeline. All our release pipelines across languages were doing full clones before these two fixes.

[benbp]

Validated against https://dev.azure.com/azure-sdk/internal/_build?definitionId=4739 which now renders valid yaml. FYI @stliu @moarychan

[ghost]

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