stop assigning roles to non-user principal

[hund030]

Purpose

Fix the azd up error in #17

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

• Get the code
• Login azd with service principal
• Run azd up

What to Check

Running azd up command should succeed.

Other Information

[anfibiacreativa]

LGTM