CLI aliases are left behind after deleting an instance from the GUI.

**Describe the bug**
When I use the command line to create aliases for an instance and later delete the instance, aliases are correctly removed. However, if I delete the instance from the GUI, aliases stay behind.

**To Reproduce**
How, and what happened?
1. `multipass launch -n foo`
1. `multipass alias foo:bar bar`
1. Delete `foo` in the GUI
1. Observe alias `bar` is still present in the output of `multipass aliases`

**Expected behavior**
Aliases for the instance would be deleted.

**Additional info**
- `multipass version`: verified in 1.16, but this is there since the GUI was implemented.

Reproduce the issue with `multipass launch -n foo`, `multipass alias foo:bar bar`, and GUI deletion, then trace the GUI instance-deletion path and compare it with the command-line deletion behavior. Done means deleting the instance from the GUI also removes `bar` from `multipass aliases`.

Written by the indexing model from the issue text.