Removing deprecated tasks

[missymessa]

Hi dotnet/spark,

The .NET Eng Services team is fully deprecating a couple of custom Azure DevOps tasks that haven't been used in many years. This PR is to clean up usage of those tasks.

Thanks!
Missy

See: dotnet/dnceng#507

We are excited to review your PR.

So we can do the best job, please check:

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