yamllint all the things

The value of `off` was taken to be a boolean, but it shouldn't be.

Synapse expects a string (currently one of: `all`, `invite`, `off`).

This also removes the `matrix_synapse_version_arm64` variable we've
been dragging around for a long time.

Since https://github.com/matrix-org/synapse/pull/11810, a multiarch Synapse
container image (for AMD64 and ARM64) is released at the same time.

Not hardcoding 'CentOS' and using the OS family ('RedHat') instead,
we now behave better on Rockylinux and AlmaLinux, etc.

With that said, we may or may not fully support CentOS/Rockylinux/AlmaLinux v8 yet.
Certain things were improved in
https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/300.

v8 support is discussed here: https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/300
Certain things (firewalld?) may still be problematic. This patch does not try to address those.
If the remaining issues are confirmed to be fixed in the future, we can mark v8 as supported.

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

Reverts b1b4ba501fdfaa, 90c9801c560b6, a3c84f78ca9c65a, ..

I haven't really traced it (yet), but on some servers, I'm observing
`ansible-playbook ... --tags=start` completing very slowly, waiting
to stop services. I can't reproduce this on all Matrix servers I manage.
I suspect that either the systemd version is to blame or that some
specific service is not responding well to some `docker kill/rm` command.

`ExecStop` seems to work great in all cases and it's what we've been
using for a very long time, so I'm reverting to that.

Updated: prometheus to v.2.33.1

Updated: nginx to 1.21.6-alpine

Updated: grafana to 8.3.4

Updated: ddclient to v3.9.1-ls77

Updated: Heisenbridge to 1.10.1

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.

docs(matrix-reminder-bot): fix help menu command

Fixing 404 error in links to main.yml

4.95-r0-1 was problematic, because `/etc/exim/exim.conf` in the
container had the wrong permissions (writable by the `exim` user).

Fixed in 697f3cff7e
which is built as 4.95-r0-2

add hookshot to README.md

4.95-r0-1 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.

Update Mjolnir from v1.2.1 to v1.3.1

Update Hydrogen from v0.2.23 to v0.2.25

link hookshot and appservice-webhooks in docs

with deprecation notice

This announces matrix-hookshot support that got added in
https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1505

add matrix-hookshot

2.2.3 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.

Upgrade Mautrix/Facebook (0.3.2 -> 0.3.3)

Not tested but shouldn't break something