Filter nupkg list so it's not duplicated when both are present in output dir

Ix.NET/Source/build-new.ps1

@@ -83,7 +83,7 @@ foreach ($nuspec in $nuspecs) {
 
 if($hasSignClientSecret) {
   Write-Host "Signing Packages" -Foreground Green
-  $nupgks = ls .\artifacts\*.nupkg | Select -ExpandProperty FullName
+  $nupgks = ls .\artifacts\*Interact*.nupkg | Select -ExpandProperty FullName
 
   foreach ($nupkg in $nupgks) {
     Write-Host "Submitting $nupkg for signing"

Rx.NET/Source/build-new.ps1

@@ -99,7 +99,7 @@ foreach ($nuspec in $nuspecs)
 
 if($hasSignClientSecret) {
   Write-Host "Signing Packages" -Foreground Green
-  $nupgks = ls .\artifacts\*.nupkg | Select -ExpandProperty FullName
+  $nupgks = ls .\artifacts\*React*.nupkg | Select -ExpandProperty FullName
 
   foreach ($nupkg in $nupgks) {
     Write-Host "Submitting $nupkg for signing"