Fix sync-variant futures_util handling in mock test; regenerate sea-orm-sync

The mock.rs test module imported `futures_util::TryStreamExt` unconditionally,
but the sync variant has no futures_util dependency (it uses `StreamShim::try_next`
instead, already gated on `feature = "sync"`). A full make-sync regen therefore
didn't compile its lib unit tests. Gate the import on `not(feature = "sync")` to
match the StreamShim pattern.

Also regenerate sea-orm-sync to catch up with recently-merged changes (#2940 docs,
#3106 sync warning, #3108 try_getable_array, non_exhaustive).