* Update matrixdotorg/mjolnir Docker tag to v1.8.1

* Upgrade Mjolnir to v1.8.3

---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Slavi Pantaleev <slavi@devture.com>

Related to 0241c71a4c

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3270#issuecomment-2143782962

With this change, it should be possible for people to adjust the Docker
dependency from `docker.service` to something else (e.g. `pkg-ContainerManager-dockerd.service`),
or to completely eliminate it by setting `devture_systemd_docker_base_docker_service_name` to an empty string.

This makes it easier for people to use the playbook against a Synology DSM server.

Please note that This Mjolnir version bump technnically is missing some extra stuff that mjolnir claims we should do but it didnt work when i tried it and well my mjolnir deployment has been running this since release day almost and its fine. No errors in log that are unexpected. (Mjolnir throws errors in the log for anyone who wonders for various things that are fine. Like if a protection is off that is an error. Its due to how matrix-bot-lib works.)

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.