Clarify which Lua scripts are incompatible with Redis Cluster

"Some of the lua scripts in this library may not be compatible with Redis Cluster."

This statement lacks specificity. Could you please clarify:

1. Which Lua scripts have Redis Cluster compatibility issues?
2. What functionality do these scripts provide?
3. What Asynq features are unavailable or limited when using Redis Cluster?

This information would help users evaluate whether Redis Cluster is suitable for their deployment.