Update wayland-backend requirement from 0.1.0 to 0.3.0

Updates the requirements on [wayland-backend](https://github.com/smithay/wayland-rs) to permit the latest version.
- [Release notes](https://github.com/smithay/wayland-rs/releases)
- [Changelog](https://github.com/Smithay/wayland-rs/blob/master/historical_changelog.md)
- [Commits](Smithay/wayland-rs@wayland-backend-v0.1.1...wayland-backend-v0.3)

---
updated-dependencies:
- dependency-name: wayland-backend
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -36,7 +36,7 @@ drm-sys = { version = "0.4.0", default-features = false, optional = true }
 memmap2 = { version = "0.7.1", optional = true }
 nix = { version = "0.26.1", optional = true }
 tiny-xlib = { version = "0.2.1", optional = true }
-wayland-backend = { version = "0.1.0", features = ["client_system"], optional = true }
+wayland-backend = { version = "0.3.0", features = ["client_system"], optional = true }
 wayland-client = { version = "0.30.0", optional = true }
 wayland-sys = "0.30.0"
 x11rb = { version = "0.12.0", features = ["allow-unsafe-code", "shm"], optional = true }