Update docs/faq.md: remove matrix_ma1sd_enabled from the suggestion to disable it

ma1sd has not been installed by default since 958d089b68d46d1810b3b508234bfc4809522f68, so it seems that the variable does not need to be mentioned here.

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

docs/faq.md

@@ -296,9 +296,6 @@ See [Serving the base domain](configuring-playbook-base-domain-serving.md).
 You can disable some not-so-important services to save on memory.
 
 ```yaml
-# An identity server is not a must.
-matrix_ma1sd_enabled: false
-
 # Disabling this will prevent email-notifications and other such things from working.
 exim_relay_enabled: false