Remove unnecessary package references (#50)

build/dependencies.props

@@ -1,7 +1,6 @@
 <Project>
   <PropertyGroup>
     <AspNetCoreVersion>2.0.0-*</AspNetCoreVersion>
-    <CoreFxVersion>4.3.0</CoreFxVersion>
     <InternalAspNetCoreSdkVersion>2.1.0-*</InternalAspNetCoreSdkVersion>
     <NETStandardImplicitPackageVersion>$(BundledNETStandardPackageVersion)</NETStandardImplicitPackageVersion>
     <TestSdkVersion>15.0.0</TestSdkVersion>