Bump Microsoft.NET.Test.Sdk from 17.14.1 to 18.0.0 (#1105)

---
updated-dependencies:
- dependency-name: Microsoft.NET.Test.Sdk
  dependency-version: 18.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

dotnet/Directory.Packages.props

@@ -101,7 +101,7 @@
     <PackageVersion Include="Microsoft.PowerFx.Interpreter" Version="1.4.0-build.20250821-1001" />
     <!-- Test -->
     <PackageVersion Include="FluentAssertions" Version="8.7.0" />
-    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.0.0" />
     <PackageVersion Include="Moq" Version="[4.18.4]" />
     <PackageVersion Include="Microsoft.SemanticKernel.Agents.Abstractions" Version="1.65.0" />
     <PackageVersion Include="Microsoft.SemanticKernel.Agents.Yaml" Version="1.65.0-beta" />