Remove unused-variable in dwio/nimble/velox/tests/VeloxWriterTests.cp…

…p +3 (#106)

Summary:
Pull Request resolved: #106

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: sdruzkin

Differential Revision: D66330541

fbshipit-source-id: 35d916c04e58c25c0cf8dac9983d7375972d8bf9

dwio/nimble/velox/tests/VeloxWriterTests.cpp

@@ -193,8 +193,6 @@ TEST_F(VeloxWriterTests, RootHasNulls) {
 }
 
 TEST_F(VeloxWriterTests, FeatureReorderingNonFlatmapColumn) {
-  const uint32_t batchSize = 10;
-
   velox::test::VectorMaker vectorMaker{leafPool_.get()};
   auto vector = vectorMaker.rowVector(
       {"map", "flatmap"},