[mlir][test] Fix -Wformat in sparse_tensor.c (NFC)

llvm-project/mlir/test/CAPI/sparse_tensor.c:50:42:
error: format specifies type 'unsigned long' but the argument has type 'MlirSparseTensorLevelType' (aka 'unsigned long long') [-Werror,-Wformat]
   50 |     fprintf(stderr, "level_type: %lu\n", lvlTypes[l]);
      |                                  ~~~     ^~~~~~~~~~~
      |                                  %llu
1 error generated.