chore(deps): bump coverlet.collector to avoid vulnerability warnings (#4547)

Author: jpnurmi

test/Directory.Build.props

@@ -65,7 +65,7 @@
     <PackageReference Include="PublicApiGenerator" Version="11.1.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.1" PrivateAssets="All" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
-    <PackageReference Include="coverlet.collector" Version="6.0.0" />
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
   </ItemGroup>
 
   <!-- these are needed because the versions that are brought in transitively have vulnerability warnings -->