vk/wsi/x11: Remove dead code

vk/wsi/x11: Remove dead code

Fix defect reported by Coverity Scan.

Logically dead code (DEADCODE)
dead_error_line: Execution cannot reach this statement: return VK_ERROR_SURFACE_LOS....

Fixes: fb9f697fbb8 ("vk/wsi/x11: move surface alpha check from get_caps to creation")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24802>