Update image version to 7.3.1

[qlikcoe]

This new version has a fix for guardian that was failing due to bad parsing of the kernel version.

Why do we need this PR?

Fixes a bug where guardian would fail to start up when the kernel version contained an unexpected suffix

Contributor Checklist

• [x] Variables are documented in the README.md
• [x] Which branch are you merging into?
  • master is for changes related to the current release of the concourse/concourse:latest image and should be good to publish immediately
  • dev is for changes related to the next release of Concourse (aka unpublished code on master in concourse/concourse)

Reviewer Checklist

This section is intended for the core maintainers only, to track review progress. Please do not fill out this section.

• [x] Code reviewed
• [x] Topgun tests run
• [x] Back-port if needed
• [x] Is the correct branch targeted? (master or dev)

[taylorsilva]

Thanks for the PR and reminder to do this. We actually have a job in CI for this: https://ci.concourse-ci.org/teams/main/pipelines/helm-chart/jobs/concourse-app-bump/

Running it now and pushing out a new version of the chart as well. I'll close this PR now.

[taylorsilva]

https://github.com/concourse/concourse-chart/commit/dd8656fd80129906d0f9b62fe059a24a337eb1df