Clarify Discord bridging docs

docs/configuring-playbook-bridge-appservice-discord.md

@@ -23,7 +23,7 @@ matrix_appservice_discord_bot_token: "YOUR DISCORD APP BOT TOKEN"
 ```
 
 4. If you've already installed Matrix services using the playbook before, you'll need to re-run it (`--tags=setup-all,start`). If not, proceed with [configuring other playbook services](configuring-playbook.md) and then with [Installing](installing.md). Get back to this guide once ready.
-5. Retrieve Discord invite link from the `{{ matrix_appservice_discord_config_path }}/invite_link` file on the server (this defaults to `/matrix/appservice-discord/config/invite_link`)
+5. Retrieve Discord invite link from the `{{ matrix_appservice_discord_config_path }}/invite_link` file on the server (this defaults to `/matrix/appservice-discord/config/invite_link`). You need to peek at the file on the server via SSH, etc., because it's not available via HTTP(S).
 6. Invite the Bot to Discord servers you wish to bridge. Administrator permission is recommended.
 7. Room addresses follow this syntax: `#_discord_guildid_channelid`. You can easily find the guild and channel ids by logging into Discord in a browser and opening the desired channel. The URL will have this format: `discordapp.com/channels/guild_id/channel_id`. Once you have figured out the appropriate room addrss, you can join by doing `/join #_discord_guildid_channelid` in your Matrix client.