store-admin ignores charm revision pinning on bundles

[Lucas Gameiro Borges]

Hello!

Not sure if this is better described as a feature request or a bug (probably the first).

Suppose I have the following charms.yaml file (this will come from a bundle file, hence the pinning):

```
applications:
[...]
  grafana-agent-k8s:
    channel: latest/edge
    charm: grafana-agent-k8s
    constraints: arch=amd64
    revision: 93
    scale: 1
[...]
```

When doing `store-admin export charms ./example.yaml`, store-admin will ignore the revision pinning (93 in this case) and will deploy the latest revision on the specified `latest/edge` channel (94 in this case):

```
Downloading grafana-agent-k8s revision 94 (edge)
  [####################################] 100%
```

Let me know if more context is needed. Thank you!