fix: enable corex topk_softmax kernel — verified correct on real BI-V100

verify_topk_softmax.py results:
  IDs match: True (0/32 mismatches)
  Max weight diff: 0.00000003
  Speedup: 2.54x vs PyTorch (0.025ms vs 0.064ms)

Previous disable was based on speculation, not measurement.

computility-run.yaml

@@ -46,6 +46,6 @@ env:
     - name: BI100_GDN_RESTORE_MODE
       value: hybrid64
     - name: BI100_MOE_COREX_TOPK_SOFTMAX
-      value: '0'
+      value: '1'
     - name: PYTORCH_CUDA_ALLOC_CONF
       value: expandable_segments:True