Bump NuGet.Protocol and NuGet.Common

Bumps [NuGet.Protocol](https://github.com/NuGet/NuGet.Client) and [NuGet.Common](https://github.com/NuGet/NuGet.Client). These dependencies needed to be updated together.

Updates `NuGet.Protocol` from 6.8.0 to 6.9.1
- [Release notes](https://github.com/NuGet/NuGet.Client/releases)
- [Commits](https://github.com/NuGet/NuGet.Client/commits)

Updates `NuGet.Common` from 6.8.0 to 6.9.1
- [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
- dependency-name: NuGet.Common
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

NStart/NStart.csproj

@@ -20,8 +20,8 @@
     <PackageReference Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.19.6" />
     <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Contracts" Version="5.0.2" />
     <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="8.0.0" />
-    <PackageReference Include="NuGet.Common" Version="6.8.0" />
-    <PackageReference Include="NuGet.Protocol" Version="6.8.0" />
+    <PackageReference Include="NuGet.Common" Version="6.9.1" />
+    <PackageReference Include="NuGet.Protocol" Version="6.9.1" />
     <PackageReference Include="SonarAnalyzer.CSharp" Version="9.19.0.84025">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>