Enable signing in 8.0-preview6

Author: joperezr

eng/pipelines/common-variables.yml

@@ -28,4 +28,4 @@ variables:
         /p:DotNetPublishUsingPipelines=true
         /p:OfficialBuildId=$(BUILD.BUILDNUMBER)
     - name: PostBuildSign
-      value: true
+      value: false