Bump System.Configuration.ConfigurationManager in /src/NHapi.Base

Bumps [System.Configuration.ConfigurationManager](https://github.com/dotnet/runtime) from 5.0.0 to 8.0.0.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v5.0.0...v8.0.0)

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

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

src/NHapi.Base/NHapi.Base.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFrameworks>net35;netstandard2.0</TargetFrameworks>
@@ -23,7 +23,7 @@
   </ItemGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
-    <PackageReference Include="System.Configuration.ConfigurationManager" Version="5.0.0" />
+    <PackageReference Include="System.Configuration.ConfigurationManager" Version="8.0.0" />
   </ItemGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'net35' ">