Fix: unet save_attn_procs at UNet2DconditionLoadersMixin (#8699)
* fix: unet save_attn_procs at custom diffusion
* style: recover unchanaged parts(max line length 119) / mod: add condition
* style: recover unchanaged parts(max line length 119)
---------
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>