Update registry1.dso.mil/ironbank/container-hardening-tools/renovate/renovate Docker tag to v38.21.4

This MR contains the following updates:

Package	Type	Update	Change
registry1.dso.mil/ironbank/container-hardening-tools/renovate/renovate		patch	38.21.0 -> 38.21.4
registry1.dso.mil/ironbank/container-hardening-tools/renovate/renovate	ironbank-base	patch	38.21.0 -> 38.21.4
registry1.dso.mil/ironbank/container-hardening-tools/renovate/renovate	final	patch	38.21.0 -> 38.21.4
registry1.dso.mil/ironbank/container-hardening-tools/renovate/renovate	stage	patch	38.21.0 -> 38.21.4

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This MR has been generated by Renovate Bot.