`ecctl deployment delete` output is unhelpful on ESS

## Readiness Checklist

- [x] I am running the latest version
- [ ] I checked the documentation and found no answer
The documentation does explain it, but I think the tool itself could be more intuitive
- [x] I checked to make sure that this issue has not already been filed
- [x] I am reporting the issue to the correct repository (for multi-repository projects)

## Expected Behavior

If I run `ecctl deployment delete` against an ESS deployment, I should get a message saying something to the effect of:

> `ecctl deployment delete` is for Elastic Cloud Enterprise only. For Elasticsearch Service (cloud.elastic.co), did you mean to use `ecctl deployment shutdown`?

## Current Behavior

```
$ ecctl deployment delete
[DELETE /deployments/{deployment_id}][404] deleteDeploymentNotFound &{Errors:[]}`.
```

The help text for this command does help (assuming I know what ECE is):

```
$ ecctl deployment delete --help
Deletes a previously shutdown deployment (Available for ECE only)

Usage:
ecctl deployment delete [flags]

Flags:
-h, --help help for delete

...
```

## Steps to Reproduce

1. Create a deployment in ESS
2. Run `ecctl deployment delete `

## Possible Solution

Alternatively, this could just do The Right Thing ™️ and shutdown/delete the deployment.

## Context

I was trying to delete a deployment I had just created in ESS (where the related UI text says "Delete deployment") and using the shell completions showed there was an `ecctl deployment delete` command, when I should have used `ecctl deployment shutdown`.

## Your Environment

* Version used: v1.5.0
* Running against Elastic Cloud SaaS or Elastic Cloud Enterprise and version: ESS
* Environment name and version (e.g. Go 1.9): go1.16.7
* Server type and version: N/A
* Operating System and version: macOS
* Link to your project: N/A

```
Version: v1.5.0
Client API Version: 2.11.0
Go version: go1.16.7
Git commit: 39dffeee
Built: Wed 18 Aug 13:33:30 2021
OS/Arch: darwin / amd64
```