chore: use latest JWA image

[DnPlas]

canonical/kubeflow-rocks#81 introduced changes in the rockcraft project that improved readability and set a standard. This commit uses the version of the container image that corresponds to that PR.

Testing instructions

With the CKF bundle:

1. Deploy the CKF 1.8 bundle
2. Build the charm in this PR and refresh jupyter-ui with it
3. Login in the dashboard and confirm the Notebooks page is working correctly by creating a Notebook and interacting with the web app.

With relevant charms:

1. Deploy istio-operators from 1.17/stable
2. Deploy the charm in this PR
3. Relate it to istio-pilot
4. Wait for the charm to become active and idle
5. Look into the container logs for any anomalies.

[kimwnasptd]

Tried to run the image locally and can confirm the app starts, and fails because it can't find K8s config.