Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1544

see Half-Shot/matrix-hookshot#167

needed for users to put private-key.pem in

see also #1527

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1498

Hopefully fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1518

https://github.com/Half-Shot/matrix-hookshot/issues/133#issuecomment-1007541580

Discussed here: https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1510

This is the equivalent of b1b4ba501f for the matrix-dendrite role.

This brings matrix-dendrite.service in line with all the other services.

We're trying to move away from implementation-specific variables,
hoping for a clean (implementation-neutral) examples/vars.yml file.

Doing this seems more reasonable and simpler.