Delete ThreadAbortException from CoreFX (#20659)

#16229

Author: jkotas

src/System.Threading.Thread/src/System.Threading.Thread.csproj

@@ -22,7 +22,6 @@
     <Compile Include="System\Threading\Thread.cs" />
     <Compile Include="System\Threading\Thread.Unix.cs" Condition="'$(TargetsUnix)' == 'true'" />
     <Compile Include="System\Threading\Thread.Windows.cs" Condition="'$(TargetsWindows)' == 'true'" />
-    <Compile Include="System\Threading\ThreadAbortException.cs" />
     <Compile Include="System\Threading\ThreadExceptionEventArgs.cs" />
   </ItemGroup>
   <ItemGroup>