This is more consistent with how we name variables. It's also less
confusing, especially given that we have `matrix_hookshot_feeds_pollTimeoutSeconds` as well.

all other bridges use that level

https://github.com/matrix-org/matrix-hookshot/releases/tag/1.4.0

based on comments in chat:
https://matrix.to/#/!TlZdPIYrhwNvXlBiEk:half-shot.uk/$RbG6itEHVV8J_u5ry1HiFdC76n19M3vmopfQOyRmkKU?via=half-shot.uk&via=matrix.org&via=envs.net

Reverts b1b4ba501fdfaa, 90c9801c560b6, a3c84f78ca9c65a, ..

I haven't really traced it (yet), but on some servers, I'm observing
`ansible-playbook ... --tags=start` completing very slowly, waiting
to stop services. I can't reproduce this on all Matrix servers I manage.
I suspect that either the systemd version is to blame or that some
specific service is not responding well to some `docker kill/rm` command.

`ExecStop` seems to work great in all cases and it's what we've been
using for a very long time, so I'm reverting to that.

see Half-Shot/matrix-hookshot#167

https://github.com/Half-Shot/matrix-hookshot/issues/133#issuecomment-1007541580