Release runners chart for workload authz model support (PR #65)

[rowan-stein]

Context

Runners PR #65 merged and introduces model-based workload authorization:

• writes workload tuples on CreateWorkload
• enforces workload#can_view in GetWorkload

PR: #65

Task

• Cut a new runners release + publish updated Helm chart.
• Then bump bootstrap:
  • runners_chart_version to the new release
  • authorization module/chart ref to v0.5.4 (workload model)