Change default for `guidance_scale`in FLUX (#9305)

To match the original code, 7.0 is too high

src/diffusers/pipelines/flux/pipeline_flux.py

@@ -536,7 +536,7 @@ class FluxPipeline(DiffusionPipeline, FluxLoraLoaderMixin, FromSingleFileMixin):
         width: Optional[int] = None,
         num_inference_steps: int = 28,
         timesteps: List[int] = None,
-        guidance_scale: float = 7.0,
+        guidance_scale: float = 3.5,
         num_images_per_prompt: Optional[int] = 1,
         generator: Optional[Union[torch.Generator, List[torch.Generator]]] = None,
         latents: Optional[torch.FloatTensor] = None,