Bump NuGet.ProjectModel from 6.0.0 to 6.5.0 (#2367)

Bumps [NuGet.ProjectModel](https://github.com/NuGet/NuGet.Client) from 6.0.0 to 6.5.0.
- [Release notes](https://github.com/NuGet/NuGet.Client/releases)
- [Commits](https://github.com/NuGet/NuGet.Client/commits)

---
updated-dependencies:
- dependency-name: NuGet.ProjectModel
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

tools/Directory.Packages.props

@@ -3,7 +3,7 @@
   <ItemGroup>
     <PackageVersion Include="McMaster.Extensions.CommandLineUtils" Version="4.0.2" />
     <PackageVersion Include="Microsoft.Build" Version="17.5.0" />
-    <PackageVersion Include="NuGet.ProjectModel" Version="6.0.0" />
+    <PackageVersion Include="NuGet.ProjectModel" Version="6.5.0" />
     <PackageVersion Include="System.IO.Abstractions" Version="19.2.4" />
   </ItemGroup>
 </Project>