Fix Epics::UpdateService to only sync changed attributes

What does this MR do and why?

When updating an epic only sync to the work item the attributes that were present as params (so the attributes that changed). This is an attempt to prevent syncing mismatches when multiple updates are occurring at or near the same time resulting in a dirty read.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

✅