embedding : adjust `n_ubatch` value (#6296)

* embedding: assign `n_ubatch` value, print error on `n_batch` overflow

* Update examples/embedding/embedding.cpp

Co-authored-by: Xuan Son Nguyen <thichthat@gmail.com>

* use %ld instead of %lld

* Revert "use %ld instead of %lld"

This reverts commit ea753ede90a86a0699f65878cc8e2020ff5eabb8.

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Co-authored-by: Xuan Son Nguyen <thichthat@gmail.com>