gbm: remove unnecessary meson include

`inc_wayland_drm` is only used if wayland is built, and it's already
added in that case a few lines below.

Fixes: a29869e872 "gbm: Don't traverse backwards for includes"
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

src/gbm/meson.build

@@ -32,7 +32,6 @@ args_gbm = []
 deps_gbm = []
 incs_gbm = [
   include_directories('main'), inc_include, inc_src, inc_loader,
-  inc_wayland_drm,
 ]
 
 if with_dri2