Update docs/configuring-playbook-bridge-mautrix-bridges.md: add a note about bridges' incompatibility with Appservice Double Puppet

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

docs/configuring-playbook-bridge-mautrix-bridges.md

@@ -143,7 +143,7 @@ After successfully enabling bridging, you may wish to set up [Double Puppeting](
 
 To set it up, you have 2 ways of going about it.
 
-#### Method 1: automatically, by enabling Appservice Double Puppet (or Shared Secret Auth)
+#### Method 1: automatically, by enabling Appservice Double Puppet or Shared Secret Auth
 
 To set up [Double Puppeting](https://docs.mau.fi/bridges/general/double-puppeting.html) enable the [Appservice Double Puppet](configuring-playbook-appservice-double-puppet.md) service for this playbook.
 
@@ -157,6 +157,9 @@ This is the recommended way of setting up Double Puppeting, as it's easier to ac
 
 Enabling the [Shared Secret Auth](configuring-playbook-shared-secret-auth.md) service works for some bridges at the time of writing, but is deprecated and will stop working in the future.
 
+<!-- TODO: remove this note if the Shared Secret Auth service has stopped working or the bridges have been removed -->
+💡 **Note**: some bridges like [the deprecated Facebook mautrix bridge](configuring-playbook-bridge-mautrix-facebook.md) and [matrix-appservice-kakaotalk](configuring-playbook-bridge-appservice-kakaotalk.md), which is partially based on the Facebook bridge, are compatible with the Shared Secret Auth service only. These bridges automatically perform Double Puppeting if [Shared Secret Auth](configuring-playbook-shared-secret-auth.md) service is configured and enabled on the server for this playbook.
+
 #### Method 2: manually, by asking each user to provide a working access token
 
 When using this method, **each user** that wishes to enable Double Puppeting needs to follow the following steps: