[deploy-sourcegraph] Use rollout strategy Recreate for stateful singleton deployments.

Created by: keegancsmith

Any of our deployments which only have one replica and a volume should use the recreate strategy. This will likely involve a migration guide or a move to a new deployment since the rollout strategy field is immutable. In the case of moving to a new deployment, care must be taken so the admin is aware that they need to port modifications from the old deployment to the new one.

See https://kubernetes.io/docs/tasks/run-application/run-single-instance-stateful-application/#updating