Bump System.Configuration.ConfigurationManager from 4.7.0 to 6.0.0

Bumps [System.Configuration.ConfigurationManager](https://github.com/dotnet/runtime) from 4.7.0 to 6.0.0.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](https://github.com/dotnet/runtime/commits/v6.0.0)

---
updated-dependencies:
- dependency-name: System.Configuration.ConfigurationManager
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

src/NHibernate/NHibernate.csproj

@@ -51,11 +51,11 @@
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp2.0'">
-    <PackageReference Include="System.Configuration.ConfigurationManager" Version="4.7.0" />
+    <PackageReference Include="System.Configuration.ConfigurationManager" Version="6.0.0" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
-    <PackageReference Include="System.Configuration.ConfigurationManager" Version="4.7.0" />
+    <PackageReference Include="System.Configuration.ConfigurationManager" Version="6.0.0" />
     <PackageReference Include="System.Reflection.Emit" Version="4.7.0" />
     <PackageReference Include="System.Reflection.Emit.Lightweight" Version="4.7.0" />
     <PackageReference Include="Microsoft.CSharp" Version="4.7.0" />