Build(deps): Bump NuGet.Protocol from 6.7.0 to 6.8.0 (#389)

Bumps [NuGet.Protocol](https://github.com/NuGet/NuGet.Client) from 6.7.0 to 6.8.0.
- [Release notes](https://github.com/NuGet/NuGet.Client/releases)
- [Commits](https://github.com/NuGet/NuGet.Client/commits)

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

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

src/Directory.Packages.props

@@ -20,7 +20,7 @@
     <PackageVersion Include="Moq" Version="4.20.69" />
     <PackageVersion Include="NLog" Version="5.2.6" />
     <PackageVersion Include="NuGet.Packaging.Core" Version="6.7.0" />
-    <PackageVersion Include="NuGet.Protocol" Version="6.7.0" />
+    <PackageVersion Include="NuGet.Protocol" Version="6.8.0" />
     <PackageVersion Include="SharpCompress" Version="0.34.2" />
     <PackageVersion Include="System.CodeDom" Version="8.0.0" />
     <PackageVersion Include="System.Security.Permissions" Version="8.0.0" />