Bump Microsoft.NET.Test.Sdk from 17.0.0 to 17.9.0 in /tests/.dependabot

Bumps [Microsoft.NET.Test.Sdk](https://github.com/microsoft/vstest) from 17.0.0 to 17.9.0.
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Changelog](https://github.com/microsoft/vstest/blob/main/docs/releases.md)
- [Commits](microsoft/vstest@v17.0.0...v17.9.0)

---
updated-dependencies:
- dependency-name: Microsoft.NET.Test.Sdk
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Directory.Packages.props

@@ -1,19 +1,19 @@
-<Project>
-  <ItemGroup>
-    <!-- ghūl MSBuild targets -->
-    <PackageVersion Include="ghul.targets" Version="1.2.4" />
-
-    <!-- ghūl language runtime -->
-    <PackageVersion Include="ghul.runtime" Version="1.1.4" />
-
-    <!-- unit test dependencies -->
-    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
-    <PackageVersion Include="Moq" Version="4.20.70" />
-    <PackageVersion Include="MSTest.TestAdapter" Version="3.2.0" />
-    <PackageVersion Include="MSTest.TestFramework" Version="3.2.0" />
-    <PackageVersion Include="FluentAssertions" Version="6.12.0" />
-    <PackageVersion Include="NSubstitute" Version="5.1.0" />
-    <PackageVersion Include="coverlet.collector" Version="6.0.0" />
-    <PackageVersion Include="coverlet.msbuild" Version="6.0.0" />
-  </ItemGroup>
+<Project>
+  <ItemGroup>
+    <!-- ghūl MSBuild targets -->
+    <PackageVersion Include="ghul.targets" Version="1.2.4" />
+
+    <!-- ghūl language runtime -->
+    <PackageVersion Include="ghul.runtime" Version="1.1.4" />
+
+    <!-- unit test dependencies -->
+    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
+    <PackageVersion Include="Moq" Version="4.20.70" />
+    <PackageVersion Include="MSTest.TestAdapter" Version="3.2.0" />
+    <PackageVersion Include="MSTest.TestFramework" Version="3.2.0" />
+    <PackageVersion Include="FluentAssertions" Version="6.12.0" />
+    <PackageVersion Include="NSubstitute" Version="5.1.0" />
+    <PackageVersion Include="coverlet.collector" Version="6.0.0" />
+    <PackageVersion Include="coverlet.msbuild" Version="6.0.0" />
+  </ItemGroup>
 </Project>