!fixup! Undo a couple of earlier fixes

- remove a duplicate `$()` setting
- correct the one remaining versioned `#if` define
  - did not make it `#if NETCOREAPP` because benchmarks test numerous .NET Core TFMs

Author: dougbu

src/ProjectTemplates/Directory.Build.props

@@ -2,9 +2,6 @@
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory)..\, Directory.Build.props))\Directory.Build.props" />
 
   <PropertyGroup>
-    <!-- TODO: Remove this when alls parts of aspnetcore switched to the net5.0 TFM. -->
-    <DefaultNetCoreTargetFramework>net5.0</DefaultNetCoreTargetFramework>
-
     <!-- The .csproj files in this folder do not actually produce .dll's. They are only present to produce .nupkgs and enable Visual Studio support -->
     <IsProjectReferenceProvider>false</IsProjectReferenceProvider>
     <HasReferenceAssembly>false</HasReferenceAssembly>

src/ProjectTemplates/build.cmd

@@ -1,3 +1,3 @@
 @ECHO OFF
 SET RepoRoot=%~dp0..\..
-%RepoRoot%\build.cmd -projects %~dp0*\*.*proj -ForceCoreMsbuild "/p:EnforceE2ETestPrerequisites=true" %*
+%RepoRoot%\build.cmd -projects %~dp0*\*.*proj "/p:EnforceE2ETestPrerequisites=true" %*

src/Shared/BenchmarkRunner/DefaultCoreConfig.cs

@@ -34,7 +34,7 @@ public DefaultCoreConfig()
                 .WithToolchain(CsProjCoreToolchain.From(new NetCoreAppSettings("netcoreapp3.0", null, ".NET Core 3.0")))
 #elif NETCOREAPP3_1
                 .WithToolchain(CsProjCoreToolchain.From(new NetCoreAppSettings("netcoreapp3.1", null, ".NET Core 3.1")))
-#elif NET5_0
+#elif NETCOREAPP5_0
                 .WithToolchain(CsProjCoreToolchain.From(new NetCoreAppSettings("net5.0", null, ".NET Core 5.0")))
 #else
 #error Target frameworks need to be updated.