chore(artifactapi): deploy v3.7.4 (#218)

## Why

artifactapi `v3.7.4` images are built and pushed; au-syd1 is on `v3.7.3`. This rolls forward to ship the terraform provider registry.

## Changes

- `api-deployment`: `artifactapi` `v3.7.3` → `v3.7.4`
- `ui-deployment`: `artifactapi-ui` `v3.7.3` → `v3.7.4`

## What's new in v3.7.4

- Local terraform repos are now a real provider registry: `/.well-known/terraform.json` + `providers.v1` versions/download with GPG-signed SHA256SUMS (#102).
- The signing key self-provisions in the DB (`signing_keys` table) — no K8s secret to mount, so no deployment wiring needed.

Once synced, `terraform init` against `source = "artifactapi.k8s.syd1.au.unkin.net/<repo>/<type>"` works.

Reviewed-on: #218
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

apps/base/artifactapi/api-deployment.yaml

@@ -35,7 +35,7 @@ spec:
               mountPath: /combined-certs
       containers:
         - name: api
-          image: git.unkin.net/unkin/artifactapi:v3.7.3
+          image: git.unkin.net/unkin/artifactapi:v3.7.4
           imagePullPolicy: IfNotPresent
           ports:
             - containerPort: 8000