Externalize tf-controller notes

The bootstrap cheatsheet doc is going away

Signed-off-by: Kingdon Barrett <kingdon@weave.works>

Author: Kingdon Barrett

content/en/blog/2022-09-05-august-update/index.md

@@ -256,7 +256,7 @@ couple of small things we landed recently:
   - Bootstrap: [Git repository access via SOCKS5 ssh
     proxy](/flux/installation/configuration/proxy-setting/#git-repository-access-via-socks5-ssh-proxy)
   - Bootstrap: [Enable notifications for third party
-    controllers](/flux/cheatsheets/bootstrap/#enable-notifications-for-third-party-controllers)
+    controllers](https://weaveworks.github.io/tf-controller/how_to/flux_receiver_and_alert/#enable-notifications-for-third-party-controllers)
 - [Flux's Work Well With section](/flux/#flux-works-well-with): find out
   how to make Flux work with your favourite other OSS software
 - Lots of new videos from GitOpsCon / KubeCon on [our resources