util/idalloc: reserving an ID that already exists should be no-op

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11493>

src/util/u_idalloc.c

@@ -99,7 +99,6 @@ util_idalloc_reserve(struct util_idalloc *buf, unsigned id)
 {
    if (id / 32 >= buf->num_elements)
       util_idalloc_resize(buf, (id / 32 + 1) * 2);
-   assert((buf->data[id / 32] & (1u << (id % 32))) == 0);
    buf->data[id / 32] |= 1u << (id % 32);
 }