Use coverlet nightlies

Directory.Build.props

@@ -120,6 +120,7 @@
       https://api.nuget.org/v3/index.json;
       <!-- Contains RemoteExecutor. Taken from: https://github.com/dotnet/runtime/blob/master/NuGet.config -->
       https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-eng/nuget/v3/index.json;
+      https://www.myget.org/F/coverlet-dev/api/v3/index.json;
     </RestoreSources>
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>$(MSBuildThisFileDirectory)shared-infrastructure/SixLabors.snk</AssemblyOriginatorKeyFile>

tests/Directory.Build.targets

@@ -28,7 +28,7 @@
     <PackageReference Update="BenchmarkDotNet" Version="0.12.1" />
     <PackageReference Update="BenchmarkDotNet.Diagnostics.Windows" Version="0.12.1" Condition="'$(OS)' == 'Windows_NT'" />    
     <PackageReference Update="Colourful" Version="2.0.5" />
-    <PackageReference Update="coverlet.collector" Version="1.3.0" PrivateAssets="All"/>
+    <PackageReference Update="coverlet.collector" Version="1.3.1-preview.27.gdd2237a3be" PrivateAssets="All"/>
     <PackageReference Update="Magick.NET-Q16-AnyCPU" Version="7.15.5" />
     <PackageReference Update="Microsoft.DotNet.RemoteExecutor" Version="5.0.0-beta.20069.1" />
     <PackageReference Update="Microsoft.NET.Test.Sdk" Version="16.7.1" />