docs: Update node onboarding public ECR URL

We were using an obfuscated public ECR name to avoid easy discovery of
nilvm Docker images prior to the nilvm repo being open sourced.

This change updates the references to the obfuscated repo name now that
the repo is open. This repo lives in our centralized platform account.

We will start to publish release candidates there starting this week.

The v0.9.0 image already lives there.

Author: jwolski2

docs/node_onboarding/README.md

@@ -91,15 +91,15 @@ be supplied to the node container to ensure authentication against MinIO is poss
 ## Launch Your Node
 
 Pull the network-compatible version of the node Docker image from Nillion's AWS ECR
-[repository](public.ecr.aws/f8o3t8b6/vkv1h9vlo); remember to append `-amd64` to the version number
+[repository](public.ecr.aws/k5d9x2g2/nilvm); remember to append `-amd64` to the version number
 tag when pulling, e.g.:
 
 > [!IMPORTANT]
 > Substitute `${VERSION}`, below, with the Node/SDK version for the corresponding network found in
 > the networks list above.
 
 ```bash
-docker pull public.ecr.aws/f8o3t8b6/vkv1h9vlo:${VERSION}-amd64
+docker pull public.ecr.aws/k5d9x2g2/nilvm:${VERSION}-amd64
 ```
 
 Then, launch the node on your infrastructure using the certificates, Docker image, node
@@ -110,7 +110,7 @@ _This command is not meant to be the exact Docker `run`  command to run on your
 illustrative for the environment variable and ECR URL._
 
 ```bash
-docker run -e CONFIG_PATH=/etc/nillion/node.yaml public.ecr.aws/f8o3t8b6/vkv1h9vlo:${VERSION}-amd64
+docker run -e CONFIG_PATH=/etc/nillion/node.yaml public.ecr.aws/k5d9x2g2/nilvm:${VERSION}-amd64
 ```
 
 All nodes present in `cluster.members` must be available before network functions can be validated.