Fix 'Updating the Agent' page with link to guide.

Author: wooly

docs/updating-agent.md

@@ -1,28 +1,5 @@
 # Updating the Agent
 
-The `buildkite-agent` is built in to the AMIs by the Packer build. The agent
-binary is downloaded from download.buildkite.com.
+:spider_web::spider_web::spider_web: Here be cobwebs! :spider_web::spider_web::spider_web:
 
-Once you have [released](https://github.com/buildkite/agent/blob/-/RELEASE.md) an updated
-version of the agent, you can incorporate it into the Elastic CI Stack
-for AWS template.
-
-See https://github.com/buildkite/elastic-ci-stack-for-aws/pull/935 for an
-example of updating the buildkite-agent.
-
-1. Create a new branch
-1. Update and commit a change to the Packer install scripts for [Linux](#linux) and [Windows](#windows) for the new version
-1. Push your branch and open a pull request
-1. Wait for CI to go green
-1. Merge
-
-## Linux
-
-Update the `AGENT_VERSION` variable in [`packer/linux/scripts/install-buildkite-agent.sh`](packer/linux/scripts/install-buildkite-agent.sh)
-to change which version is installed during the Packer build for the Linux AMI.
-
-## Windows
-
-Update the `AGENT_VERSION` variable in [`packer/windows/scripts/install-buildkite-agent.ps1`](packer/windows/scripts/install-buildkite-agent.ps1)
-to change which version is installed during the Packer build for the Windows
-AMI.
+The docs that used to be here now live in the [Agent Release Process](https://guide.buildkite.net/engineering/teams/pipelines/agent-release-process/) page of the guide.