Bump Microsoft.NET.Test.Sdk from 16.7.1 to 16.8.0

Bumps [Microsoft.NET.Test.Sdk](https://github.com/microsoft/vstest) from 16.7.1 to 16.8.0.
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Commits](microsoft/vstest@v16.7.1...v16.8.0)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

src/Directory.Build.props

@@ -28,7 +28,7 @@
         <PackageVersion_MicrosoftExtensions>3.0.0</PackageVersion_MicrosoftExtensions>
         <PackageVersion_MsBuild>16.7.0</PackageVersion_MsBuild>
 
-        <PackageVersion_MicrosoftTestSdk>16.7.1</PackageVersion_MicrosoftTestSdk>
+        <PackageVersion_MicrosoftTestSdk>16.8.0</PackageVersion_MicrosoftTestSdk>
         <PackageVersion_NSubstitute>4.2.2</PackageVersion_NSubstitute>
         <PackageVersion_CoverletMsBuild>2.9.0</PackageVersion_CoverletMsBuild>
         <PackageVersion_NUnit>3.12.0</PackageVersion_NUnit>