This PR fixes a panic that would occur when trying to submit feedback
while within a shared project.

There may be a way we want to support this in the future, but for now we
just show a toast letting the user know this is not supported:

<img width="415" alt="Screenshot 2024-01-05 at 2 46 02 PM"
src="https://github.com/zed-industries/zed/assets/1486634/d3eff4d9-90ba-4257-9857-19b1bc933cf3">

Release Notes:

- Fixed a panic when attempting to open the feedback modal while in a
shared project.