[master] Update dependencies from dotnet/arcade

[dotnet-maestro]

This pull request updates the following dependencies

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

• Build: 20190824.1
• Date Produced: 8/24/2019 12:51 PM
• Commit: a7b5eb8de300b6a30bd797c4ecc8769f7028aeec
• Branch: refs/heads/master
• Updates:
  • Microsoft.DotNet.Arcade.Sdk -> 1.0.0-beta.19424.1

[dotnet-maestro]

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