Merge pull request #11036 from brianrob/remove_eventcounter

Remove EventCounter from System.Private.CoreLib

Author: brianrob

src/mscorlib/shared/System.Private.CoreLib.Shared.projitems

@@ -407,7 +407,6 @@
   <ItemGroup>
     <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\ActivityTracker.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\EventActivityOptions.cs" />
-    <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\EventCounter.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\EventDescriptor.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\EventProvider.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Diagnostics\Tracing\EventSource.cs" />