[pod-gateway]: Bump image versions

[bjw-s]

Description of the change

Updates the default images used by pod-gateway to the latest ones.

Benefits

Users don't have to manually update the images to get the latest version.

Possible drawbacks

Applicable issues

• fixes #1684

Additional information

Checklist

• [ ] Title of the PR starts with chart name (e.g. [home-assistant])
• [ ] Chart version bumped in Chart.yaml according to semver.
• [ ] Chart artifacthub.io/changes changelog annotation has been updated in Chart.yaml. See Artifact Hub documentation for more info.
• [ ] Variables have been documented in the values.yaml file.

[djfinnoy]

Would be nice if the image tag defaulted to chart.appVersion when .Values.image.tag is undefined.