Permissions, when set in the template, will be augmented rahter than replaced when using matrix_mautrix_signal_configuration_extension_yaml. Therefore, permissions shall only be set in the defaults/vars.yml or in the HS specific vars.yml file
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`.
