I believe `specialized-workers` is a better name than `room-workers`,
because when enabled, 4 different types of specialized workers are
created:

- Room workers
- Sync workers
- Client readers
- Federation readers

Only one of these is called room-workers.

In the future, more specialized workers may be added, making the
`room-workers` preset name an even poorer choice.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3100