Update DEVELOPMENT_MAITENANCE.md - haproxy

Items to review and edit in DEVELOPMENT_MAITENANCE.md by section:

• How to upgrade the HAProxy Package chart

This needs to be updated. For example, it contains references to using Meld to run a diff on the upstream chart.

• Testing a new HAProxy version

No edits needed.

• Modifications made to upstream chart

The securityContext: value in chart/values.yaml does not match what is specified here. Investigate this and update the documentation as needed.