Bump NuGet.Versioning from 6.8.0 to 6.9.1 in /Src/NuGetDefense.Lib

Bumps [NuGet.Versioning](https://github.com/NuGet/NuGet.Client) 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.Versioning
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Src/NuGetDefense.Lib/NuGetDefense.Lib.csproj

@@ -36,7 +36,7 @@
             <PrivateAssets>all</PrivateAssets>
             <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
         </PackageReference>
-        <PackageReference Include="NuGet.Versioning" Version="6.8.0" />
+        <PackageReference Include="NuGet.Versioning" Version="6.9.1" />
         <PackageReference Include="NuGetDefense.Core" Version="2.0.7" />
         <PackageReference Include="NuGetDefense.GitHubAdvisoryDatabase" Version="2.0.5" />
         <PackageReference Include="NuGetDefense.NVD" Version="2.1.0" />