wayland-protocols: Update version from 1.12 to 1.18

GTK+ 3.24.11 requires at least version 1.14, so update to the latest and
greatest release.

The [releases page][1] also links to the announcements in the list
archives. From the [1.18 announcement][2].

> This version comes with documentational clarifications, bug fixes and
> minor additions to existing protocols. See the commit log for details.

[1]: https://wayland.freedesktop.org/releases.html
[2]: https://lists.freedesktop.org/archives/wayland-devel/2019-July/040756.html

wayland-protocols.be0

@@ -1,6 +1,6 @@
 #!/usr/bin/env beesh
 
-# BEE_VERSION wayland-protocols-1.12-0
+# BEE_VERSION wayland-protocols-1.18-0
 
 ## this file was created by bee init and should be executed to build a
 ## bee-package. (Additional hints are located at the end of this file.)