[llvm] [Github] Only delete branches seen previously in pruning workflow (PR #181430)

[via llvm-commits]

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@@ -2,9 +2,14 @@
 import sys
 import os
 import logging
+import zipfile
+import io
+import urllib.request
 
 import github
 
+GITHUB_WORKFLOW_ID = 57373867111
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cmtice wrote:

This doesn't need to be secret in any way, does it?

https://github.com/llvm/llvm-project/pull/181430