Add user_aliases to the options for deleting users

[dulle-braze]

Pull Request/Issue Resolution

Description of Change:

Adding documentation to show customers that they can delete users by specifying an array of user alias objects in the user_aliases key.

Reason for Change:

This change was implemented quietly last sprint.

This functionality is live, so this can be merged at any time.

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[EmilyNecciai]

lgtm!