[release/3.1.4xx] Update dependencies from nuget/nuget.client

[dotnet-maestro]

This pull request updates the following dependencies

From https://github.com/NuGet/NuGet.Client

• Subscription: 7c87b7fc-1d68-435f-7062-08d7e6f19e0b
• Build: 5.7.0.6609
• Date Produced: 5/6/2020 11:02 PM
• Commit: 12a375a8a02764b772a20371abaf797639a7f961
• Branch: dev
• Updates:
  • NuGet.Build.Tasks: from 5.7.0-preview.1.6592 to 5.7.0-preview.1.6609

[dotnet-maestro]

Auto-Merge Status

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

• ✔️ Standard Merge Policies Succeeded - Successful checks: .NET Core CLI CI, .NET Core CLI CI (Build Darwin Build_Release), .NET Core CLI CI (Build Linux Build_Ubuntu_14_04_Release_x64), .NET Core CLI CI (Build Linux Build_LinuxPortable_NoSuffix_Release_x64), .NET Core CLI CI (Build Linux Build_LinuxPortable_Release_x64), .NET Core CLI CI (Build Linux Build_Linux_musl_Debug_x64), .NET Core CLI CI (Build Linux Build_Rhel_6_Debug_x64), .NET Core CLI CI (Build Linux Build_Rhel_7_2_Release_x64), .NET Core CLI CI (Build Linux Build_Debian_jessie_Debug_x64), .NET Core CLI CI (Build Linux Build_CentOS_7_1_Debug_x64), .NET Core CLI CI (Build Linux Build_OpenSUSE_42_3_Debug_x64), .NET Core CLI CI (Build Linux Build_Fedora_27_Debug_x64), .NET Core CLI CI (Build Linux Build_Ubuntu_18_04_Debug_x64), .NET Core CLI CI (Build Linux Build_Ubuntu_16_04_Debug_x64), .NET Core CLI CI (Build Windows_NT Build_Release_x64), .NET Core CLI CI (Build Windows_NT Build_DropSuffix_Release_x64), .NET Core CLI CI (Build Windows_NT Build_ES_Debug_x64), .NET Core CLI CI (Build Windows_NT Build_Debug_x86)
• ✔️ Standard Merge Policies Succeeded - No reviews have requested changes.
• ✔️ Standard Merge Policies Succeeded - No version downgrade detected.