Bump NuGet.Protocol from 6.4.0 to 6.4.2 in /src/Dotnet.Deps.Core

Bumps [NuGet.Protocol](https://github.com/NuGet/NuGet.Client) from 6.4.0 to 6.4.2.
- [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] <support@github.com>

src/Dotnet.Deps.Core/Dotnet.Deps.Core.csproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
@@ -17,7 +17,7 @@
     <PackageReference Include="NuGet.Configuration" Version="6.4.0" />
     <PackageReference Include="NuGet.Packaging" Version="6.4.0" />
     <PackageReference Include="NuGet.Packaging.Core" Version="6.4.0" />
-    <PackageReference Include="NuGet.Protocol" Version="6.4.0" />
+    <PackageReference Include="NuGet.Protocol" Version="6.4.2" />
     <PackageReference Include="ShellProgressBar" Version="5.2.0" />
   </ItemGroup>
 </Project>