Related to 3daf14d695

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/4549

Other homeserver implementations (not just Synapse) may also support MSC2246
(https://github.com/matrix-org/matrix-spec-proposals/pull/2246)
and may also be eligible. For now, it's only enabled for Synapse.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/4549

Related to:

- 83165d77fa
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1493
- d166a90514

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/4550

Update dependency etherpad to v2.4.2-2

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/4542

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/4539

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1493 and d166a90514

The MAS docs recommend this option for migrated Synapse passwords
to work: https://element-hq.github.io/matrix-authentication-service/setup/migration.html#local-passwords

Closes #4232

This should bring better compatibility with future Ansible versions,
one of which will some day drop support for accessing facts via the global namespace.

Ref: https://github.com/geerlingguy/ansible-role-docker/pull/513

Related to https://github.com/element-hq/synapse/pull/18759

Currently problematic (leading to failures to start for Synapse) because of:
https://github.com/element-hq/synapse/pull/18759#issuecomment-3172744530