chore(deps): update nuget monorepo to v6.8.0 (#911)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Coby Allred <cobyallred@gmail.com>

Directory.Packages.props

@@ -28,8 +28,8 @@
     <PackageVersion Include="MSTest.TestFramework" Version="3.1.1" />
     <PackageVersion Include="Newtonsoft.Json" Version="13.0.3" />
     <PackageVersion Include="Newtonsoft.Json.Schema" Version="3.0.15" />
-    <PackageVersion Include="NuGet.ProjectModel" Version="6.7.0" />
-    <PackageVersion Include="NuGet.Versioning" Version="6.7.0" />
+    <PackageVersion Include="NuGet.ProjectModel" Version="6.8.0" />
+    <PackageVersion Include="NuGet.Versioning" Version="6.8.0" />
     <PackageVersion Include="packageurl-dotnet" Version="1.0.0" />
     <PackageVersion Include="Polly" Version="8.2.0" />
     <PackageVersion Include="SemanticVersioning" Version="2.0.2" />