Unpin winit version

The new version of winit fixes an important bug for macOS Sonoma,
and the bugvix for the workaround won't happen before winit 0.29.
The branch that port to winit 0.29 already removed the workaround

Fixes #3559

(cherry picked from commit 89c269e)

internal/backends/winit/Cargo.toml

@@ -44,8 +44,7 @@ lyon_path = "1.0"
 once_cell = "1.5"
 pin-weak = "1"
 scoped-tls-hkt = "0.1"
-# Pinned due to https://github.com/slint-ui/slint/issues/2424
-winit = { version = "=0.28.6", default-features = false }
+winit = { version = "0.28.7", default-features = false }
 instant = "0.1"
 raw-window-handle = { version = "0.5", features = ["alloc"] }
 scopeguard =  { version = "1.1.0", default-features = false }