fix typo in conversion script
# What does this PR do?

Fix typo in `convert_fsmt_original_pytorch_checkpoint_to_pytorch.py`

## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).


## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors which may be interested in your PR.
@stas00

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Wonderful! Thank you for this fix, @tagucci! 

(I tweaked your PR to run `make style` to appease to auto-formatters to have CI pass)