Fix staged John cleanup for repeated ISO builds

iso/builder/build.sh

@@ -249,9 +249,10 @@ rm -f \
     "${OVERLAY_STAGE_DIR}/usr/local/bin/bee-nccl-gpu-stress" \
     "${OVERLAY_STAGE_DIR}/usr/local/bin/john" \
     "${OVERLAY_STAGE_DIR}/usr/local/lib/bee/bee-gpu-burn-worker" \
-    "${OVERLAY_STAGE_DIR}/usr/local/lib/bee/john" \
     "${OVERLAY_STAGE_DIR}/usr/local/bin/bee-smoketest" \
     "${OVERLAY_STAGE_DIR}/usr/local/bin/all_reduce_perf"
+rm -rf \
+    "${OVERLAY_STAGE_DIR}/usr/local/lib/bee/john"
 
 # Remove NVIDIA-specific overlay files for non-nvidia variants
 if [ "$BEE_GPU_VENDOR" != "nvidia" ]; then