Changed `matrix_mautrix_signal_docker_image_force_pull` to `matrix_mautrix_signal_daemon_docker_image_force_pull` when force pulling the daemon

We'll be adding `.timer` units later on, so it's good to be
more explicit.

While it's kind of nice having it, it's also somewhat raw
and unnecessary.

Having a good default and not even mentioning it seems better
for most users.

People who need a more exposed bridge (rare) can use
override the default configuration using
`matrix_mautrix_signal_configuration_extension_yaml`.