notin -> eq for PostBuildSign conditional (#43850)

.azure/pipelines/ci.yml

@@ -43,7 +43,7 @@ variables:
   value:  AspNetCore
 - name: _PublishUsingPipelines
   value: true
-- ${{ if or(startswith(variables['Build.SourceBranch'], 'refs/heads/release/'), startswith(variables['Build.SourceBranch'], 'refs/heads/internal/release/'), notin(variables['Build.Reason'], 'Manual')) }}:
+- ${{ if or(startswith(variables['Build.SourceBranch'], 'refs/heads/release/'), startswith(variables['Build.SourceBranch'], 'refs/heads/internal/release/'), eq(variables['Build.Reason'], 'Manual')) }}:
   - name: PostBuildSign
     value: false
 - ${{ else }}: