vulkan/wsi: Remove duplicate NULL check

Fix defect reported by Coverity Scan.

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

Fixes: eadc64ab24 ("vulkan/wsi/display: do not dereference a NULL pointer")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23415>

src/vulkan/wsi/wsi_common_display.c

@@ -303,9 +303,6 @@ wsi_display_alloc_connector(struct wsi_display *wsi,
    if (!connector)
       return NULL;
 
-   if (!connector)
-      return NULL;
-
    connector->id = connector_id;
    connector->wsi = wsi;
    connector->active = false;