Cleanup csproj after removing support for .NET Framework (#230)

Cleanup csproj after removing NET Framework support.
#224

Author: metoule

src/DynamicExpresso.Core/DynamicExpresso.Core.csproj

@@ -20,11 +20,6 @@
     <VersionSuffix></VersionSuffix>
   </PropertyGroup>
 
-
-  <ItemGroup Condition=" $(TargetFramework.StartsWith('net4')) ">
-    <Reference Include="Microsoft.CSharp" />
-  </ItemGroup>
-
   <ItemGroup Condition=" $(TargetFramework.StartsWith('netstandard2')) ">
     <PackageReference Include="Microsoft.CSharp" Version="4.7.0" />
   </ItemGroup>

test/DynamicExpresso.UnitTest/DynamicExpresso.UnitTest.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
 	<PropertyGroup>
-		<TargetFrameworks>netcoreapp5.0;netcoreapp3.1;net462</TargetFrameworks>
+		<TargetFrameworks>net5.0;netcoreapp3.1;net462</TargetFrameworks>
 
 		<IsPackable>false</IsPackable>
 	</PropertyGroup>
@@ -12,10 +12,6 @@
 		<PackageReference Include="NUnit3TestAdapter" Version="3.9.0" />
 	</ItemGroup>
 
-  <ItemGroup Condition=" $(TargetFramework.StartsWith('net4')) ">
-		<Reference Include="Microsoft.CSharp" />
-	</ItemGroup>
-
 	<ItemGroup>
 	  <ProjectReference Include="..\..\src\DynamicExpresso.Core\DynamicExpresso.Core.csproj" />
 	</ItemGroup>