Fix publishing pipeline to download prebuilds from current branch (#899)

* Initial plan

* Fix publishing pipeline to use current branch for prebuild artifact lookup

Co-authored-by: rzhao271 <7199958+rzhao271@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: rzhao271 <7199958+rzhao271@users.noreply.github.com>

Author: Copilot

publish.yml

@@ -46,7 +46,7 @@ extends:
               project: 'Monaco'
               definition: '647'
               buildVersionToDownload: 'latestFromBranch'
-              branchName: 'refs/heads/main'
+              branchName: '$(Build.SourceBranch)'
               artifactName: 'prebuilds-$(Build.SourceVersion)'
               targetPath: 'prebuilds'
           - pwsh: |
@@ -69,7 +69,7 @@ extends:
               project: 'Monaco'
               definition: '647'
               buildVersionToDownload: 'latestFromBranch'
-              branchName: 'refs/heads/main'
+              branchName: '$(Build.SourceBranch)'
               artifactName: 'prebuilds-$(Build.SourceVersion)'
               targetPath: 'prebuilds'
           - bash: chmod +x prebuilds/darwin-*/spawn-helper