Remove unused-variable in velox/buffer/tests/BufferTest.cpp +8 (#11421)

Summary:
Pull Request resolved: #11421

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]]`.

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Reviewed By: palmje

Differential Revision: D65282800

fbshipit-source-id: 3ebdc85005aa8a250db6c5e72826d18a7a95f926

velox/functions/lib/RowsTranslationUtil.h

@@ -41,9 +41,9 @@ SelectivityVector toElementRows(
   auto rawNulls = arrayBaseVector->rawNulls();
   auto rawSizes = arrayBaseVector->rawSizes();
   auto rawOffsets = arrayBaseVector->rawOffsets();
-  const auto sizeRange =
+  VELOX_DEBUG_ONLY const auto sizeRange =
       arrayBaseVector->sizes()->template asRange<vector_size_t>().end();
-  const auto offsetRange =
+  VELOX_DEBUG_ONLY const auto offsetRange =
       arrayBaseVector->offsets()->template asRange<vector_size_t>().end();
 
   SelectivityVector elementRows(size, false);