Fix dependency from EventLog to TraceSource ref (#56417)

* Fix dependency from EventLog to TraceSource ref

This regressed with 663c40d. Reference projects should never reference source projects. This is one of the reasons why slngen creates different solution files now.

* Update Microsoft.Extensions.DependencyInjection.Abstractions.csproj

Author: ViktorHofer

src/libraries/Microsoft.Extensions.DependencyInjection.Abstractions/ref/Microsoft.Extensions.DependencyInjection.Abstractions.csproj

@@ -11,6 +11,6 @@
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0' or
                         $([MSBuild]::GetTargetFrameworkIdentifier('$(TargetFramework)')) == '.NETFramework'">
     <PackageReference Include="System.Threading.Tasks.Extensions" Version="$(SystemThreadingTasksExtensionsVersion)" />
-    <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Bcl.AsyncInterfaces\src\Microsoft.Bcl.AsyncInterfaces.csproj" />
+    <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Bcl.AsyncInterfaces\ref\Microsoft.Bcl.AsyncInterfaces.csproj" />
   </ItemGroup>
 </Project>

src/libraries/System.Diagnostics.EventLog/ref/System.Diagnostics.EventLog.csproj

@@ -10,7 +10,7 @@
     <ProjectReference Include="$(LibrariesProjectRoot)System.Security.Permissions\ref\System.Security.Permissions.csproj" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">
-    <ProjectReference Include="$(LibrariesProjectRoot)System.Diagnostics.TraceSource\src\System.Diagnostics.TraceSource.csproj" />
+    <ProjectReference Include="$(LibrariesProjectRoot)System.Diagnostics.TraceSource\ref\System.Diagnostics.TraceSource.csproj" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1'">
     <Reference Include="System.ComponentModel.Primitives" />
@@ -19,4 +19,4 @@
     <Reference Include="System.Runtime" />
     <Reference Include="System.Runtime.InteropServices" />
   </ItemGroup>
-</Project>
+</Project>