Update handle single blocks on _convert_xlabs_flux_lora_to_diffusers (#9915)
* Update handle single blocks on _convert_xlabs_flux_lora_to_diffusers to fix bug on updating keys and old_state_dict
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Co-authored-by: raul_ar <raul.moreno.salinas@autoretouch.com>
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>