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.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1605

Fixes a regression introduced in ccb85b31a4. The
`docker.io/devture/email2matrix:1.0.2` container image was faulty due to
this 49f966d6cc

1.0.2 is the first container image tag that is available as a multi-arch image
with support for linux/amd64, linux/arm64/v8 (arm64) and linux/arm/v7 (arm32),
so self-building is no longer necessary on all these platforms.

Signed-off-by: Ahmad Haghighi <haghighi@fedoraproject.org>

This is both for consistency with 93cc71cb69976c
and for making things more obvious.