Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2068

* matrix-backup-borg: added option for unencrypted repo access

* matrix-backup-borg: fixed requiring password for unencrypted repos; changed variable name

* matrix-backup-borg: add unknown_unencrypted_repo_access_is_ok to config.yaml.j2

* matrix-backup-borg: cleanup comments

* matrix-backup-borg: add documentation regarding unencrypted repos

* matrix-backup-borg: add readability and ease of use to code

* matrix-backup-borg: fix wording in defaults/main.yml comment

* matrix-backup-borg: add quotes to docs

* Indicate the variable to use

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

People often report and ask about these "failures".
More-so previously, when the `docker kill/rm` output was collected,
but it still happens now when people do `systemctl status
matrix-something` and notice that it says "FAILURE".

Suppressing to avoid further time being wasted on saying "this is
expected".

* add borg backup

* lint fix

* add exlclude patterns

* missed in the #1726 fix for honoroit

* feedback

* Fix indentation

* feedback

* feedback

* feedback

Co-authored-by: Slavi Pantaleev <slavi@devture.com>