ci/check-cherry-picks: add staging-next as pickable branches (#412306)

# Make sure we are inside the nixpkgs repo, even when called from outside

cd "$(dirname "${BASH_SOURCE[0]}")"

PICKABLE_BRANCHES="master release-??.?? staging-??.?? haskell-updates python-updates"

PICKABLE_BRANCHES="master staging release-??.?? staging-??.?? haskell-updates python-updates staging-next staging-next-??.??"

problem=0

# Not everyone calls their remote "origin"