Update docs/configuring-playbook-bridge-mautrix-slack.md

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

The instruction has been obsolete since 25b4006035

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

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

@@ -58,10 +58,10 @@ ansible-playbook -i inventory/hosts setup.yml --tags=setup-all,ensure-matrix-use
 
 ## Usage
 
-1. Start a chat with `@slackbot:example.com` (where `example.com` is your base domain, not the `matrix.` domain).
-2. If you would like to login to Slack using a token, send the `login-token` command, otherwise, send the `login-password` command. Read [here](https://docs.mau.fi/bridges/go/slack/authentication.html) on how to retrieve your token and cookie token.
-3. The bot should respond with "Successfully logged into <email> for team <workspace>"
-4. Now that you're logged in, you can send `help` to the bot to see the available commands.
-5. Slack channels should automatically begin bridging if you authenticated using a token. Otherwise, you must wait to receive a message in the channel if you used password authentication.
+To use the bridge, you need to start a chat with `@slackbot: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/slack/authentication.html).
+You can then follow instructions on the bridge's [official documentation on Authentication](https://docs.mau.fi/bridges/go/slack/authentication.html).
+
+If you authenticated using a token, the recent chats will be bridged automatically (depending on the `conversation_count` setting). Otherwise (i.e. with App login), the chats the bot is in will be bridged automatically.
+
+Send `help` to the bot to see the available commands.