Screenshot does not contains the `bevy_egui` GUI in 0.15 anymore

## Bevy version

0.15

## What you did

I ported my application to Bevy 0.15. Now the screenshot does not contains the `bevy_egui` GUI anymore. It did in Bevy 0.14.

## What went wrong

I was expecting the screenshot to capture everything in the primary window like it was in 0.14.

## Additional information

I tried to change the system order to make sure the command to spawn the `Screenshot` component was done after drawing the GUI and after some `bevy_egui` internal systems, and every order I thought could fix the issue but without any luck.

I also opened a `bevy_egui` issue thinking this might be a issue related to this plugin: https://github.com/vladbat00/bevy_egui/issues/329

I do not know what to try or what to look for in order to try new workaround. Any suggestion is welcome.