Fix missing winit feature in egui_glow

[bash]

Since #4849, running ./scripts/check.sh fails with:

...

error[E0277]: the trait bound `ActiveEventLoop: raw_window_handle::borrowed::HasDisplayHandle` is not satisfied
  --> crates/egui_glow/src/winit.rs:43:13
   |
43 |             event_loop,
   |             ^^^^^^^^^^ the trait `raw_window_handle::borrowed::HasDisplayHandle` is not implemented for `ActiveEventLoop`
   |
   = help: the following other types implement trait `raw_window_handle::borrowed::HasDisplayHandle`:
             raw_window_handle::borrowed::DisplayHandle<'a>
             &H
             &mut H
   = note: required for the cast from `&ActiveEventLoop` to `&dyn raw_window_handle::borrowed::HasDisplayHandle`

This PR adds the missing rwh_06 to the winit dependency (in egui-glow).

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