ci/check-cherry-picks: allow cherry-picking from haskell-updates and python-updates

Those are protected branches, which can't be force pushed to - so the
commits will remain. Thus, we can also backport from them.

ci/check-cherry-picks.sh

@@ -11,7 +11,7 @@ fi
 # Make sure we are inside the nixpkgs repo, even when called from outside
 cd "$(dirname "${BASH_SOURCE[0]}")"
 
-PICKABLE_BRANCHES=${PICKABLE_BRANCHES:-master staging release-??.?? staging-??.??}
+PICKABLE_BRANCHES="master release-??.?? staging-??.?? haskell-updates python-updates"
 problem=0
 
 # Not everyone calls their remote "origin"