Clarify using multiple schedulers with the same configuration

Author: rosa

README.md

@@ -408,6 +408,8 @@ Tasks are enqueued at their corresponding times by the scheduler, and each task
 
 It's possible to run multiple schedulers with the same `recurring_tasks` configuration, for example, if you have multiple servers for redundancy, and you run the `scheduler` in more than one of them. To avoid enqueuing duplicate tasks at the same time, an entry in a new `solid_queue_recurring_executions` table is created in the same transaction as the job is enqueued. This table has a unique index on `task_key` and `run_at`, ensuring only one entry per task per time will be created. This only works if you have `preserve_finished_jobs` set to `true` (the default), and the guarantee applies as long as you keep the jobs around.
 
+**Note**: a single recurring schedule is supported, so you can have multiple schedulers using the same schedule, but not multiple schedulers using different configurations.
+
 Finally, it's possible to configure jobs that aren't handled by Solid Queue. That is, you can have a job like this in your app:
 ```ruby
 class MyResqueJob < ApplicationJob