Update docs for mautrix-meta bridges: add links to the official documentation on authentication

Based on d33701428d/bridges/go/meta/authentication.md

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

docs/configuring-playbook-bridge-mautrix-meta-instagram.md

@@ -66,4 +66,4 @@ ansible-playbook -i inventory/hosts setup.yml --tags=setup-all,ensure-matrix-use
 
 To use the bridge, you need to start a chat with `@instagrambot:example.com` (where `example.com` is your base domain, not the `matrix.` domain).
 
-You can learn more here about authentication from the bridge's [official documentation on Authentication](https://docs.mau.fi/bridges/go/meta/authentication.html).
+You can then follow instructions on the bridge's [official documentation on Authentication](https://docs.mau.fi/bridges/go/meta/authentication.html).

docs/configuring-playbook-bridge-mautrix-meta-messenger.md

@@ -79,8 +79,6 @@ ansible-playbook -i inventory/hosts setup.yml --tags=setup-all,ensure-matrix-use
 
 To use the bridge, you need to start a chat with `@messengerbot:example.com` (where `example.com` is your base domain, not the `matrix.` domain). Note that the user ID of the bridge's bot is not `@facebookbot:example.com`.
 
-You then need to send `login` to the bridge bot and follow the instructions.
+You can then follow instructions on the bridge's [official documentation on Authentication](https://docs.mau.fi/bridges/go/meta/authentication.html).
 
-Given that the bot is configured in `messenger` [bridge mode](#bridge-mode) by default, you will need to log in to [messenger.com](https://messenger.com/) (not `facebook.com`!) and obtain the cookies from there as per [the bridge's authentication instructions](https://docs.mau.fi/bridges/go/meta/authentication.html).
-
-You can learn more here about authentication from the bridge's [official documentation on Authentication](https://docs.mau.fi/bridges/go/meta/authentication.html).
+**Note**: given that the bot is configured in `messenger` [bridge mode](#bridge-mode) by default, you will need to log in to [messenger.com](https://messenger.com/) (not `facebook.com`!) and obtain the cookies from there.