Non-open-access backend used in fractional-gates.ipynb

[frankharkins]

The fractional gates notebook uses a backend that is not available on ibm-q/open/main. We should switch this notebook to use an open-access backend so all users can run the code examples on the page.

[Eric-Arellano]

@frankharkins this causes CI to break in #2491, meaning CI is broken on main. Are you able to either please fix the issue this week or should we move the notebook to not testable? If the fix isn't super hard, the former is preferred.