gdk-wayland: fix docs url
use stable release instead of git
authors = ["The gtk-rs Project Developers"]
build = "build.rs"
description = "FFI bindings of GDK4 Wayland"
-documentation = "https://gtk-rs.org/gtk4-rs/git/docs/gdk4_wayland_sys/"
+documentation = "https://gtk-rs.org/gtk4-rs/stable/latest/docs/gdk4_wayland_sys/"
edition = "2018"
homepage = "http://gtk-rs.org/"
keywords = ["gdk4", "gdk4-wayland", "ffi", "gtk-rs", "gnome"]
