Not doing {% if matrix_admin %} checks in the YAML also fixes some issues
with indentation being incorrect sometimes.

This should be backward compatible, except for mautrix-signal's case
where `matrix_mautrix_signal_bridge_permissions` previously existed
as a string, not a dictionary. `tasks/validate_config.yml` will catch
the problem an even provide a quick fix.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1939

While it's kind of nice having it, it's also somewhat raw
and unnecessary.

Having a good default and not even mentioning it seems better
for most users.

People who need a more exposed bridge (rare) can use
override the default configuration using
`matrix_mautrix_signal_configuration_extension_yaml`.