Bump coverlet.msbuild from 3.2.0 to 6.0.0

Bumps [coverlet.msbuild](https://github.com/coverlet-coverage/coverlet) from 3.2.0 to 6.0.0.
- [Release notes](https://github.com/coverlet-coverage/coverlet/releases)
- [Commits](coverlet-coverage/coverlet@v3.2.0...v6.0.0)

---
updated-dependencies:
- dependency-name: coverlet.msbuild
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Refit.Tests/Refit.Tests.csproj

@@ -13,7 +13,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="coverlet.msbuild" Version="3.2.0" />
+    <PackageReference Include="coverlet.msbuild" Version="6.0.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.5.0" />
     <PackageReference Include="xunit" Version="2.4.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5" />