doc: Fix wayland release notes
The core_only kwarg got renamed to include_core_only.
-## Added core_only arg to wayland.scan_xml.
+## Added `include_core_only` arg to wayland.scan_xml.
The `scan_xml` function from the wayland module now has an optional bool
-argument `core_only`, so that headers generated by wayland-scanner now
+argument `include_core_only`, so that headers generated by wayland-scanner now
only include `wayland-client-core.h` instead of `wayland-client.h`.
