[release/5.0.1xx-preview8] Update dependencies from dotnet/roslyn

[dotnet-maestro]

This pull request updates the following dependencies

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

• Subscription: e251dd77-ab9f-49fc-4299-08d828bd4fbd
• Build: 20200723.6
• Date Produced: 7/23/2020 11:17 PM
• Commit: fc5f6179a2521062cb61d44d0e41e1ef596907d9
• Branch: refs/heads/release/dev16.8-preview1-vs-deps

• Updates:
  • Microsoft.Net.Compilers.Toolset: from 3.8.0-1.20373.2 to 3.8.0-1.20373.6

[dotnet-maestro]

Auto-Merge Status

This pull request has been merged because the following merge policies have succeeded.

• ✔️ Standard Merge Policies Succeeded - Successful checks: dotnet-sdk-public-ci, dotnet-sdk-public-ci (Build Darwin Build_Release), dotnet-sdk-public-ci (Build Ubuntu_16_04 Build_Release), dotnet-sdk-public-ci (Build Darwin Build_Debug), dotnet-sdk-public-ci (Build Ubuntu_16_04 Build_Debug), dotnet-sdk-public-ci (Build Windows_NT_TestAsTools Build_Debug), dotnet-sdk-public-ci (Build Windows_NT_FullFramework Build_Release), dotnet-sdk-public-ci (Build Windows_NT_FullFramework Build_Debug), dotnet-sdk-public-ci (Build Windows_NT Build_Release), dotnet-sdk-public-ci (Build Windows_NT Build_Debug)
• ✔️ Standard Merge Policies Succeeded - No reviews have requested changes.
• ✔️ Standard Merge Policies Succeeded - No version downgrade detected.