Build(deps): Bump NuGet.Packaging.Core from 6.6.1 to 6.7.0 (#354)

Bumps [NuGet.Packaging.Core](https://github.com/NuGet/NuGet.Client) from 6.6.1 to 6.7.0.
- [Release notes](https://github.com/NuGet/NuGet.Client/releases)
- [Commits](https://github.com/NuGet/NuGet.Client/commits)

---
updated-dependencies:
- dependency-name: NuGet.Packaging.Core
  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>

src/Directory.Packages.props

@@ -19,7 +19,7 @@
     <PackageVersion Include="Mono.Cecil" Version="0.11.5" />
     <PackageVersion Include="Moq" Version="4.20.1" />
     <PackageVersion Include="NLog" Version="5.2.3" />
-    <PackageVersion Include="NuGet.Packaging.Core" Version="6.6.1" />
+    <PackageVersion Include="NuGet.Packaging.Core" Version="6.7.0" />
     <PackageVersion Include="NuGet.Protocol" Version="6.6.1" />
     <PackageVersion Include="SharpCompress" Version="0.33.0" />
     <PackageVersion Include="System.CodeDom" Version="7.0.0" />