Remove or change references to Projects.Upload

The line at https://gitlab.com/gitlab-org/cli/-/blob/main/commands/release/releaseutils/upload/upload.go#L84 is now setting off the linter because Projects.UploadFile is now deprecated.

Our API docs recommend switching to UploadProjectMarkdown, but that's intended for Markdown files only - this function was built around other filetypes.

We should try to find an actual way to do this or we might just have to remove the feature (which I don't think is working anyway)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information