Hi there,
To me this looks like a quoting issue.
From the error message, I think the agent is trying to run a program called "git pull", rather than trying to run a program called "git" while passing "pull" as the first argument.
I don't know why behaviour would have changed from GoCD version 21.2 to 23.3, but I recommend looking at your job definitions to see if they need to be restructured to properly pass the instructions to the agent.
Hope this helps,
Jason Smyth