Bump coverlet packages to v8 (#212)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

tests/Prometheus.Client.DependencyInjection.Tests.csproj

@@ -7,11 +7,11 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
-    <PackageReference Include="coverlet.collector" Version="6.0.4">
+    <PackageReference Include="coverlet.collector" Version="8.0.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="coverlet.msbuild" Version="6.0.4">
+    <PackageReference Include="coverlet.msbuild" Version="8.0.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>