Trim more legacy support out of csproj

Author: sblom

src/json-ld.net/json-ld.net.csproj

@@ -13,7 +13,6 @@ Implements the W3C JSON-LD 1.0 standard.</Description>
     <PackageProjectUrl>https://github.com/linked-data-dotnet/json-ld.net/</PackageProjectUrl>
     <PackageLicenseUrl>https://raw.githubusercontent.com/linked-data-dotnet/json-ld.net/master/LICENSE</PackageLicenseUrl>
     <PackageTargetFallback Condition=" '$(TargetFramework)' == 'netstandard1.1' ">$(PackageTargetFallback);dnxcore50;portable-net45+win8</PackageTargetFallback>
-    <NetStandardImplicitPackageVersion Condition=" '$(TargetFramework)' == 'netstandard1.1' ">1.6.0</NetStandardImplicitPackageVersion>
     <GenerateAssemblyConfigurationAttribute>false</GenerateAssemblyConfigurationAttribute>
     <GenerateAssemblyCompanyAttribute>false</GenerateAssemblyCompanyAttribute>
     <GenerateAssemblyProductAttribute>false</GenerateAssemblyProductAttribute>