If you create a project:

resource "vercel_project" "example" {
  name      = "example"
  framework = "nextjs"
}

And change it to (assuming you actually have the GitHub app setup in the account)

resource "vercel_project" "example" {
  name      = "example"
  framework = "nextjs"

  git_repository = {
    type              = "github"
    repo              = "vercel/example"
    production_branch = "main"
  }
}

The provider wants to do a delete/create action, rather than an update.

Is this intended? Manually adding the GitHub app to the project and then running the terraform plan again showed that the API was able to update the project without recreation.