Investigate possible dead code in `handle_uncovered_swap_chains`

This seems to make sense, although we have code in the camera driver render graph system that attempts to handle the case where we acquire but do no work on a swapchain. See `handle_uncovered_swap_chains`. In theory, with this change, that code path is no longer necessary? (NB: Reading the code, I remember we used to have code that handled the case where you do have a camera but did no work, I think that is now handled by `view_target.needs_present` which tracks whether we ever did work on a view target).

If so, we should remove the `handle_uncovered_swap_chains` system.

_Originally posted by @tychedelia in https://github.com/bevyengine/bevy/pull/23276#pullrequestreview-3919432498_