Remove disk cleanup step from build_GPU workflow

Removed pre-job step for cleaning up disk space.

.github/workflows/build_GPU.yml

@@ -22,26 +22,6 @@ jobs:
         run: |
           version=$(grep -oP "subgen_version\s*=\s*'\K[^']+" subgen.py)
           echo "version=$version" >> "$GITHUB_ENV"
-          
-      - name: Pre-job:free disk space
-        shell: bash
-        run: |
-          set -euo pipefail
-          echo "Disk before cleanup:"
-          df -h /
-
-          # Prune buildx builder data and docker caches
-          sudo docker builder prune --all --force || true
-          sudo docker system prune -af --volumes || true
-
-          # Remove temp files
-          sudo rm -rf /tmp/* || true
-
-          # Remove old buildkit cache if present
-          sudo rm -rf /var/lib/docker/buildkit || true
-
-          echo "Disk after cleanup:"
-          df -h /
 
       - name: Login to Docker Hub
         uses: docker/login-action@v3