text: Title: SDXL InPainting: Mask blur option is negated by forced binarization.
  Body: The SDXL InPainting pipeline's documentation suggests using `pipeline.mask_processor.blur()` for creating soft masks, but this functionality is effectively broken due to the implementation order. Please let me know if I'm missing something here. Based on my testing, whether I use a blurred mask or blur them with the built in method, they still show a solid seam as if there was no blur applied.
  
  The mask processor is initialized with forced binarization:
  
  ```
  self.mask_processor = VaeImageProcessor(
      vae_scale_factor=self.vae_scale_factor,
      do_normalize=False,
      do_binarize=True,  # Forces binarization
      do_convert_grayscale=True
  )
  ```
  
  When processing masks, any blur effect is applied before binarization, which then converts all values back to pure black and white, completely negating the blur effect (if I'm not mistaken). The VaeImageProcessor defaults binarize to false, but when masks are initialized it sets binarize to true.
  
  Relevant files:
  diffusers/stable_diffusion_xl/pipeline_stable_diffusion_xl_inpaint.py[326]
  diffusers/image_processor.py[88][276][523]
  
  ### Reproduction
  
  Inpaint pipeline config using either your own blurred image or the built in blur method according to documentation. It's fairly self explanatory and I don't have a minimal script to share.
  
  ### System Info
  
  diffusers==0.32.2
  
  ### Who can help?
  
  @yiyixuxu @DN6 