dri: Stop answering DRI_IMAGE_ATTRIB_FORMAT

External users only care about FourCC, and they can already query that
directly.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30245>

src/gallium/frontends/dri/dri2.c

@@ -1293,9 +1293,6 @@ static bool
 dri2_query_image_common(__DRIimage *image, int attrib, int *value)
 {
    switch (attrib) {
-   case __DRI_IMAGE_ATTRIB_FORMAT:
-      *value = image->dri_format;
-      return true;
    case __DRI_IMAGE_ATTRIB_WIDTH:
       *value = image->texture->width0;
       return true;