Update Microsoft.NET.Test.Sdk requirement from 17.7.* to 17.8.*

Updates the requirements on [Microsoft.NET.Test.Sdk](https://github.com/microsoft/vstest) to permit the latest version.
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Changelog](https://github.com/microsoft/vstest/blob/main/docs/releases.md)
- [Commits](microsoft/vstest@v17.7.0...v17.8.0)

---
updated-dependencies:
- dependency-name: Microsoft.NET.Test.Sdk
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Directory.Build.props

@@ -33,7 +33,7 @@
     <JetBrainsAnnotationsVersion>2023.3.*</JetBrainsAnnotationsVersion>
     <MongoDBDriverVersion>2.21.*</MongoDBDriverVersion>
     <SourceLinkVersion>1.1.*</SourceLinkVersion>
-    <TestSdkVersion>17.7.*</TestSdkVersion>
+    <TestSdkVersion>17.8.*</TestSdkVersion>
     <XunitVersion>2.5.*</XunitVersion>
   </PropertyGroup>