SYS-696 cleanup after recent updates

[instantlinux]

Summary of Changes

• Update helm chart versions for updated images - data-sync, dovecot, mythtv-backend, postfix-python, proftpd, spamassassin
• Add --ignore-unfixed trivy flag for debian builds -- debian distro causes trivy to alert on a lot of false-positives
• Skip headscale/db.sqlite-shm in data-sync image -- frequently updated file that is regenerated on restart
• Bump docker image version for pipeline stages
• Jump through the hoops needed to stuff the newest deep-linked README.md into the dockerhub API for each image

Why is this change being made?

Four images wouldn't build properly on last pipeline run; the helm chart versions hadn't all ben updated

How was this tested? How can the reviewer verify your testing?

Manual testing

Completion checklist

• The pull request is linked to all related issues
• This change has unit test coverage
• Documentation has been updated
• Dependencies have been updated and verified