Bump System.CodeDom from 5.0.0 to 6.0.0 (#106)

* Bump System.CodeDom from 5.0.0 to 6.0.0

Bumps [System.CodeDom](https://github.com/dotnet/runtime) from 5.0.0 to 6.0.0.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v5.0.0...v6.0.0)

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

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

* Remove netcoreapp2.1 target framework, not supported anymore

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Gregorius Soedharmo <arkatufus@yahoo.com>

src/Akka.MultiNode.SampleMultiNodeTests/Akka.MultiNode.SampleMultiNodeTests.csproj

@@ -2,7 +2,7 @@
     <Import Project="..\common.props" />
 
     <PropertyGroup>
-        <TargetFrameworks>netcoreapp2.1;$(NetCoreTestVersion);$(NetTestVersion)</TargetFrameworks>
+        <TargetFrameworks>$(NetCoreTestVersion);$(NetTestVersion)</TargetFrameworks>
     </PropertyGroup>
 
     <ItemGroup>

src/common.props

@@ -12,7 +12,7 @@
     <XunitVersion>2.4.1</XunitVersion>
     <TestSdkVersion>17.1.0</TestSdkVersion>
     <HyperionVersion>0.9.12</HyperionVersion>
-    <CodeDomVersion>5.0.0</CodeDomVersion>
+    <CodeDomVersion>6.0.0</CodeDomVersion>
     <TeamCityVersion>3.0.13</TeamCityVersion>
     <SystemRuntimeLoaderVersion>4.3.0</SystemRuntimeLoaderVersion>
     <DependencyModelVersion>5.0.0</DependencyModelVersion>