The current service doesn't play too nice with Sway when it is started
from [sway service](https://github.com/xdbob/sway-services).
Waybar is started before the system has a display.
```
Nov 30 22:11:23 ansan waybar[1352]: Unable to init server: Could not
connect: Connection refused
Nov 30 22:11:23 ansan waybar[1352]: cannot open display:
Nov 30 22:11:23 ansan systemd[1306]: waybar.service: Main process
exited, code=exited, status=1/FAILURE
Nov 30 22:11:23 ansan systemd[1306]: waybar.service: Failed with result
'exit-code'.
```
Restarting the service after the system has been initialized works nicely,
so this restart rule should do the trick without tinkering with the
target.