This removes the following Redis config settings from Workhorse:

- KeepAlivePeriod
- ReadTimeout
- WriteTimeout

These settings have been broken for 4 years (since
0e777472). If you tried
setting them in config.toml, Workhorse would fail to start up.

Because this is a major failure (failing to start) and no-one has
fixed it after 4 years I think we can conclude nobody uses these
settings and we can remove them.