Runner Configuration Docs doesn't explain how to apply config changes
### Problem to solve
The Runner [Advanced Configuration](https://docs.gitlab.com/runner/configuration/advanced-configuration.html) documentation doesn't explain how changes to the configuration file (`config.toml`) are applied.
Does the runner need to be restarted or is there a command similar to `gitlab-ctl reconfigure`?
### Further details
(None.)
### Proposal
Answer the question above and make sure the documentation gives this answer as well.
### Who can address the issue
Any engineer who is familiar with the Runner configuration.
### Other links/references
issue