Chore: Fix deployment types in telemetry (#256)

## Description

<!-- description here -->

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

Keeping env var name consistent between deployment repos

---

## Checklist

<!--
Kubernetes, both Kustomize and Helm, and Docker Compose MUST be kept in
sync.
You should not merge a change here without a corresponding change in the
other repositories,
unless it is specific to this deployment type. If uneeded, add link or
explanation of why it is not needed here.
-->

- [ ] Update
[CHANGELOG.md](https://github.com/sourcegraph/deploy-sourcegraph-k8s/blob/main/CHANGELOG.md)
- [ ] Update [K8s Upgrade
notes](https://github.com/sourcegraph/sourcegraph/blob/main/doc/admin/updates/kubernetes.md)
- [x] Kustomiz-specific changes
- [ ] Update sister repository:
[deploy-sourcegraph-helm](https://github.com/sourcegraph/deploy-sourcegraph-helm)
- [ ] Update sister repository:
[deploy-sourcegraph-docker](https://github.com/sourcegraph/deploy-sourcegraph-docker)
- [ ] Verify all images have a valid tag and SHA256 sum

## Test plan

Test in Looker

<!--
As part of SOC2/GN-104 and SOC2/GN-105 requirements, all pull requests
are REQUIRED to
provide a "test plan". A test plan is a loose explanation of what you
have done or
implemented to test this, as outlined in our Testing principles and
guidelines:

https://docs.sourcegraph.com/dev/background-information/testing_principles
  Write your test plan here after the "Test plan" header.
-->

Author: marcleblanc2

components/clusters/k3s/kustomization.yaml

@@ -10,4 +10,4 @@ configMapGenerator:
   - name: sourcegraph-frontend-env
     behavior: merge
     literals:
-      - DEPLOY_TYPE=k3s
+      - DEPLOY_TYPE=kustomize

components/patches/frontend-vars.yaml

@@ -3,5 +3,5 @@ kind: ConfigMap
 metadata:
   name: sourcegraph-frontend-env
 data:
-  DEPLOY: kustomize
+  DEPLOY_TYPE: kustomize
   # Add env vars for frontend service below