Upgrade metal crate from git to released 0.29 on crates.io (#240)

All our changes were merged upstream and finally made it into the `0.29`
release on crates.io, via gfx-rs/metal-rs#327.

Author: MarijnS95

Cargo.toml

@@ -34,7 +34,7 @@ egui = { version = ">=0.24, <=0.27", optional = true, default-features = false }
 egui_extras = { version = ">=0.24, <=0.27", optional = true, default-features = false }
 
 [target.'cfg(any(target_os = "macos", target_os = "ios"))'.dependencies]
-metal = { version = "0.28.0", git = "https://github.com/gfx-rs/metal-rs", rev = "0d6214f", default-features = false, features = ["link", "dispatch"], optional = true }
+metal = { version = "0.29.0", default-features = false, features = ["link", "dispatch"], optional = true }
 
 [target.'cfg(windows)'.dependencies]
 # Only needed for public-winapi interop helpers