Remove local kustomization.yaml files from deployment process

[nawatts]

Currently, creating a deployment using deployctl creates a local kustomization.yaml file and applying the deployment applies it using kubectl.

https://github.com/broadinstitute/gnomad-browser/blob/95f5d24f540f8132dc9cf546226ae9581bb095bb/deploy/deployctl/subcommands/browser_deployments.py#L31-L35

However, the only thing that changes is the image tag used. Deployment could be changed to a one step process where deployctl accepts an image tag as a CLI argument and generates the kustomization.yaml file.