index resources workflow: Invalid choice: nextclade

Error seen in [index resources](https://github.com/nextstrain/nextstrain.org/actions/runs/21055529292/job/60550971666#step:6:15) on 2026-01-15. ``` main.js: error: argument "--collections": Invalid choice: nextclade (choose from [core, staging]) usage: main.js [-h] [--local] [--collections <name> [<name> ...]] [--resourceTypes <name> [<name> ...]] [--save-inventories] --output <json> [--indent] [--gzip] ```