remove FSDP prefix when using save_pretrained with FSDP2 (#40207)
* remove FSDP prefix when using save_pretrained with FSDP2
* Fix: use removeprefix correctly
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Co-authored-by: Matej Sirovatka <54212263+S1ro1@users.noreply.github.com>
Co-authored-by: S1ro1 <matej.sirovatka@gmail.com>