Chore: Fix deployment types in telemetry (#4454)

### Description

Linear issue [REL-812: Update deployment
types](https://linear.app/sourcegraph/issue/REL-812/update-deployment-types)

Instances with deployment type "Kubernetes" are too vague to be useful
in telemetry. Setting this now, so that we can start identifying these
usefully in Telemetry as customers upgrade their legacy Kustomize
instances >= 6.2.0

<!-- description here -->

> NOTE:

### Checklist

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- [ ]
[CHANGELOG.md](https://github.com/sourcegraph/sourcegraph/blob/main/CHANGELOG.md)
updated
- [ ] [K8s Upgrade notes
updated](https://github.com/sourcegraph/sourcegraph/blob/main/doc/admin/updates/kubernetes.md)
- [x] Sister
[deploy-sourcegraph-k8s](https://github.com/sourcegraph/deploy-sourcegraph-docker)
change:
- [ ] Sister
[deploy-sourcegraph-docker](https://github.com/sourcegraph/deploy-sourcegraph-docker)
change:
- [ ] All images have a valid tag and SHA256 sum
- [x] I acknowledge that
[deploy-sourcegraph-k8s](https://github.com/sourcegraph/deploy-sourcegraph-k8s)
is now the preferred Kubernetes deployment repository

### Test plan

Test in Looker

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Author: marcleblanc2

base/frontend/sourcegraph-frontend.Deployment.yaml

@@ -104,6 +104,8 @@ spec:
               fieldPath: status.hostIP
         - name: OTEL_EXPORTER_OTLP_ENDPOINT
           value: http://$(OTEL_AGENT_HOST):4317
+        - name: DEPLOY_TYPE
+          value: "legacy-kustomize"
         terminationMessagePolicy: FallbackToLogsOnError
         livenessProbe:
           httpGet: