`roles/matrix-synapse/vars/workers.yml` has not been updated here,
because running `roles/matrix-synapse/files/workers-doc-to-yaml.awk`
seems to cause some trouble with the current `workers.md` file
available at https://github.com/matrix-org/synapse/raw/master/docs/workers.md,
namely lots of:

> FIXME: ADDITIONAL CONDITIONS REQUIRED: to be enabled manually

lines and commented out regex lines.

This is something that remains to be investigated/fixed.