* Use ElementTheme.colors.bgCanvasDefault instead of MaterialTheme.colorScheme.background
Even if the value is the same, we should use color from ElementTheme.
* Remove background management of ElementCallActivity. It does not work as expected and also changing theme during a call would require to load the url again with the new theme.
* Do not use isSystemInDarkTheme() directly.
* Use bgSubtleSecondary for background color of Preview.
* Use default colors for Preview.
* Fix copy paste issue.
* Update screenshots
---------
Co-authored-by: ElementBot <android@element.io>
8c64b842a5