Resolve "500 Internal Server Error: Deleting branch of deleted project"

What does this MR do?

Previously we were returning from our API projects that were marked for deletion. This MR removes project marked from deletion from the API. This should fix #50678 (closed) and some other cases such as #50949 (closed) #50678 (closed).

Note for the reviewer

The changes affects also the ProjectsFinder which is widely used inside the application. The changes now applies the without_deleted scope to all the results; I think there is no use case when we need to show project marked for deletion but if there are any we need to change this scope in order to be a new parameter.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides

Closes #50678 (closed)