also change docker image publishing to use branch

Author: JunAishima

.github/workflows/publish-ghcr.yml

@@ -4,7 +4,7 @@ name: Create and publish a Docker image
 # Configures this workflow to run every time a change is pushed to the branch called `release`.
 on:
   push:
-    branches: ['main']
+    branches: ['prefect3-pixi-upgrade']
 
 # Defines two custom environment variables for the workflow. These are used for the Container registry domain, and a name for the Docker image that this workflow builds.
 env: