remove XL checkpoint download (OOMKilled build, training uses standard turbo)

Dockerfile

@@ -89,11 +89,6 @@ RUN python3 -c "from huggingface_hub import snapshot_download; \
     snapshot_download('ACE-Step/Ace-Step1.5', local_dir='/app/checkpoints', \
     ignore_patterns=['*.md', '*.txt', '.gitattributes'])"
 
-# XL turbo checkpoint for training (matches XL GGUF used for inference)
-RUN python3 -c "from huggingface_hub import snapshot_download; \
-    snapshot_download('ACE-Step/acestep-v15-xl-turbo', local_dir='/app/checkpoints/acestep-v15-xl-turbo', \
-    ignore_patterns=['*.md', '*.txt', '.gitattributes'])"
-
 # Copy application files
 COPY app.py /app/app.py
 COPY train_engine.py /app/train_engine.py