clients/window: clean up xkb compose data

This fixes ASan report:
	SUMMARY: AddressSanitizer: 151360 byte(s) leaked in 451 allocation(s).

The leaks can be observed if you let weston-desktop-shell start fully
before shutting down Weston. Many simple test suite tests are too fast
to hit this, or do not even use desktop-shell.

This clean-up code is copied from keyboard_handle_keymap().

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

clients/window.c

@@ -5878,6 +5878,8 @@ output_get_model(struct output *output)
 static void
 fini_xkb(struct input *input)
 {
+	xkb_compose_state_unref(input->xkb.compose_state);
+	xkb_compose_table_unref(input->xkb.compose_table);
 	xkb_state_unref(input->xkb.state);
 	xkb_keymap_unref(input->xkb.keymap);
 }