build(deps): Bump NuGet.Protocol in /wpf/getting-started/ReactiveDemo (#670)

Bumps [NuGet.Protocol](https://github.com/NuGet/NuGet.Client) from 6.3.0 to 6.3.1.
- [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
...

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

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

Author: dependabot[bot]

wpf/getting-started/ReactiveDemo/ReactiveDemo.csproj

@@ -8,7 +8,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="NuGet.Protocol" Version="6.3.0" />
+    <PackageReference Include="NuGet.Protocol" Version="6.3.1" />
     <PackageReference Include="ReactiveUI.WPF" Version="18.*" />
   </ItemGroup>
 </Project>