Fix git push in CI

Using a direct URL doesn't work in CI, because there authentication
works with a token that's associated with a specific named remote

Assume the origin remote exists instead, which is generally what it
would be locally, and is also what actions/checkout uses

Author: infinisil

scripts/retire.sh

@@ -112,7 +112,7 @@ for login in *; do
       trap 'trace git checkout "$mainBranch" && trace git branch -D "$branchName"' exit
       trace git rm "$login"
       trace git commit -m "Automatic retirement of @$login"
-      effect git push -f -u [email protected]:"$ORG"/"$MEMBER_REPO" "$branchName"
+      effect git push -f -u origin "$branchName"
       {
         echo "This is an automated PR to retire @$login as a Nixpkgs committers due to not using their commit access for 1 year."
         echo ""