V-Sync swapchain image count setting is read after start

[Kaleb-Reid]

Your Godot version: latest git commit at the time of writing

Issue description: I believe that the note saying that the property is only read when the project starts is incorrect, as after looking through the Vulkan driver at least, the setting is read every time the swap chain is resized. This could be forced immediately by running something like DisplayServer.window_set_vsync_mode(DisplayServer.window_get_vsync_mode()). I'm not sure of every case or the most elegant way to note it in the documentation, but I was under the impression that changing the swap chain image count would require a restart.

URL to the documentation page: https://docs.godotengine.org/en/latest/classes/class_projectsettings.html#class-projectsettings-property-rendering-rendering-device-vsync-swapchain-image-count