Remove unused-variable in deeplearning/fbgemm/fbgemm_gpu/fb/test/prep…

…roc_test_reference.hpp +3 (pytorch#3412)

Summary:
Pull Request resolved: pytorch#3412

X-link: facebookresearch/FBGEMM#500

LLVM-15 has a warning `-Wunused-variable` which we treat as an error because it's so often diagnostic of a code issue. Unused variables can compromise readability or, worse, performance.

This diff either (a) removes an unused variable and, possibly, it's associated code or (b) qualifies the variable with `[[maybe_unused]]`.

#buildsonlynotests - Builds are sufficient

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Differential Revision: D66330353

fbshipit-source-id: a97406b3116d6a6b860a53db9f371247db04c1b2

fbgemm_gpu/src/embedding_inplace_ops/embedding_inplace_update_test.cpp

@@ -65,7 +65,7 @@ void test_embedding_inplace_update() {
     }
     int n = folly::Random::rand32() % 10 + 5;
     std::set<int32_t> rows;
-    for (const auto j : c10::irange(n)) {
+    for ([[maybe_unused]] const auto j : c10::irange(n)) {
       rows.insert(folly::Random::rand32() % total_rows);
     }
     std::string update_row_idx_str = "";