Update gatekeeper to v3.19.1

This MR contains the following updates:

Package	Update	Change
gluon	patch	0.5.15 -> 0.5.19
ironbank/opensource/openpolicyagent/gatekeeper (source)	minor	v3.18.2 -> v3.19.1
registry1.dso.mil/ironbank/opensource/kubernetes/kubectl (source)	patch	v1.32.3 -> v1.32.4
registry1.dso.mil/ironbank/opensource/openpolicyagent/gatekeeper (source)	minor	v3.18.2 -> v3.19.1

Closes issue #278 (closed)

Complete MR checklist

Assignee

• Followed upgrade instructions outlined in docs/DEVELOPMENT_MAINTENANCE.md
• Update Docs with new/updated steps as needed
• Tested and Validated Changes made with supporting info like logs or screenshots from test pipelines

Add supporting info below

see comments for screenshots

Reviewer only

• Tested and Validated changes

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Upgrade Notices

N/A