Add back win8 helix queue

Author: HaoK

eng/targets/Helix.Common.props

@@ -27,6 +27,7 @@
 
   <!-- daily scheduled only queues -->
   <ItemGroup Condition="'$(IsWindowsOnlyTest)' != 'true' AND '$(TargetArchitecture)' == 'x64' AND '$(IsHelixDaily)' == 'true'">
+    <HelixAvailableTargetQueue Include="Windows.81.Amd64.Open" Platform="Windows" />
     <HelixAvailableTargetQueue Include="Ubuntu.1804.Amd64.Open" Platform="Linux" />
     <HelixAvailableTargetQueue Include="OSX.1014.Amd64.Open" Platform="Linux" />
     <HelixAvailableTargetQueue Include="Centos.7.Amd64.Open" Platform="Linux" />