Get rid of 'Detected a linear (sRGBA aware) framebuffer. egui prefers Rgba8Unorm or Bgra8Unorm' warning

Unless I'm highly mistaken, this warning https://github.com/emilk/egui/blame/f2ce6424f3a32f47308fb9871d540c01377b2cd9/crates/egui-wgpu/src/renderer.rs#L346-L351 is quite outdated right? egui can handle srgb render attachments perfectly fine, it just means you don't apply `linear_from_gamma_rgb` in the shader.

Start in crates/egui-wgpu/src/renderer.rs around lines 346-351 and inspect why the linear sRGBA framebuffer warning is emitted. Verify the warning against egui's handling of sRGB render attachments and the shader behavior described in the issue. Done means the outdated warning is removed or corrected without affecting valid sRGB rendering.

Written by the indexing model from the issue text.