Regenerate cargo-expand snapshots for added safe_add tests

The test_add_u64 and test_import_contract crates now define
`safe_add`/`safe_add_two` (and `safe_add_with`/`safe_add_with_two` on
the importer side) returning `Result<u64, Error>` / `Result<u64, MyError>`,
so their `tests-expanded/*.rs` snapshots — checked by the
`expand-test-wasms` CI job — needed regeneration.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: willemneal