repart: if partition already exists, required size may not be multiple of grain size

See partition_min_size_with_padding().
Fixes #37178.

(cherry picked from commit cb109e00c45c8e92b1020e6249aac4a212e7f72d)
(cherry picked from commit 4e6d6d885d320c27deb63b8a5ae5b330c00a174c)
(cherry picked from commit ee9434f7022fdbb48a2f1466d9531da2a30c35cd)

Author: yuwata

src/partition/repart.c

@@ -836,7 +836,6 @@ static bool context_allocate_partitions(Context *context, uint64_t *ret_largest_
 
                 /* How much do we need to fit? */
                 required = partition_min_size_with_padding(context, p);
-                assert(required % context->grain_size == 0);
 
                 for (size_t i = 0; i < context->n_free_areas; i++) {
                         a = context->free_areas[i];