Update README_sd3.md (#8490)

becasue in  Readme  it was not correct
train_dreambooth_sd3.py to train_dreambooth_lora_sd3

Author: AMEERAZAM08

examples/dreambooth/README_sd3.md

@@ -120,7 +120,7 @@ export MODEL_NAME="stabilityai/stable-diffusion-3-medium-diffusers"
 export INSTANCE_DIR="dog"
 export OUTPUT_DIR="trained-sd3-lora"
 
-accelerate launch train_dreambooth_sd3.py \
+accelerate launch train_dreambooth_lora_sd3.py \
   --pretrained_model_name_or_path=$MODEL_NAME  \
   --instance_data_dir=$INSTANCE_DIR \
   --output_dir=$OUTPUT_DIR \
@@ -138,4 +138,4 @@ accelerate launch train_dreambooth_sd3.py \
   --validation_epochs=25 \
   --seed="0" \
   --push_to_hub
-```
+```