SSH Keys getting overwritten

If you've already successfully run though the FS ref arch automation, then re-run terraform apply without any changes, then SSH keys are getting overwritten as though they've changed (but they haven't). This causes a destroy/reapply, which fails b/c the keys are in use, which leads you to a broken TF state that is unrecoverable.

You end up stuck with something like this:

```
╷
│ Error: [ERROR] Error deleting SSH Key : SSH-key still in use by 3 instance(s). First instance ID: 02r7_5b38d6f9-03ba-47d2-818a-dd5449722076
│ {
│ "StatusCode": 409,
│ "Headers": {
│ "Cache-Control": [
│ "max-age=0, no-cache, no-store, must-revalidate"
│ ],
│ "Cf-Cache-Status": [
│ "DYNAMIC"
│ ],
│ "Cf-Ray": [
│ "6fe07d101fbd0668-IAD"
│ ],
│ "Content-Length": [
│ "197"
│ ],
│ "Content-Type": [
│ "application/json; charset=utf-8"
│ ],
│ "Date": [
│ "Mon, 18 Apr 2022 21:28:09 GMT"
│ ],
│ "Expect-Ct": [
│ "max-age=604800, report-uri=\"https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct\""
│ ],
│ "Expires": [
│ "-1"
│ ],
│ "Pragma": [
│ "no-cache"
│ ],
│ "Server": [
│ "cloudflare"
│ ],
│ "Strict-Transport-Security": [
│ "max-age=31536000; includeSubDomains"
│ ],
│ "X-Content-Type-Options": [
│ "nosniff"
│ ],
│ "X-Request-Id": [
│ "c1045fd8-eec4-4036-b3e7-43e758d20bf4"
│ ],
│ "X-Xss-Protection": [
│ "1; mode=block"
│ ]
│ },
│ "Result": {
│ "errors": [
│ {
│ "code": "conflict_field",
│ "message": "SSH-key still in use by 3 instance(s). First instance ID: 02r7_5b38d6f9-03ba-47d2-818a-dd5449722076"
│ }
│ ],
│ "trace": "c1045fd8-eec4-4036-b3e7-43e758d20bf4"
│ },
│ "RawResult": null
│ }
```