Fix variable used in signing (#11361) (#11362)

Co-authored-by: Jacob Viau <[email protected]>

Author: Francisco-Gamino

eng/ci/templates/official/jobs/build-artifacts-windows.yml

@@ -88,7 +88,7 @@ jobs:
   - template: ci/sign-files.yml@eng
     parameters:
       displayName: Sign NugetPackages
-      folderPath: $(nuget_package_path)
+      folderPath: $(nuget_drop_path)
       pattern: '*.nupkg'
       signType: nuget