Remove unused dependency for netstandard2.0.

Author: Tsar Nikolay

src/log4net/log4net.csproj

@@ -153,7 +153,6 @@
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">
     <PackageReference Include="System.Configuration.ConfigurationManager" Version="4.5.0" />
-    <PackageReference Include="System.Reflection" Version="4.3.0" />
   </ItemGroup>
   <ItemGroup>
     <BootstrapperPackage Include="Microsoft.Net.Client.3.5">