[main] Update dependencies from dotnet/arcade

[dotnet-maestro[bot]]

This pull request updates the following dependencies

From https://github.com/dotnet/arcade

• Subscription: 92c25bea-b43c-4b62-6774-08d8f479343c

• Build: 20210408.2

• Date Produced: 4/8/2021 8:26 PM

• Commit: 814754c257edd24aeff89615106e4557d07632d8

• Branch: refs/heads/main

• Updates:

  • Microsoft.DotNet.Arcade.Sdk: from 6.0.0-beta.21205.1 to 6.0.0-beta.21208.2
  • Microsoft.DotNet.Helix.Sdk: from 6.0.0-beta.21205.1 to 6.0.0-beta.21208.2