Fix a warning (treated as error) caused by type mismatch.

Summary: Closes https://github.com/facebook/rocksdb/pull/4032

Differential Revision: D8573061

Pulled By: riversand963

fbshipit-source-id: 112324dcb35956d6b3ec891073f4f21493933c8b

tools/db_stress.cc

@@ -2864,7 +2864,7 @@ class NonBatchedOpsStressTest : public StressTest {
       std::terminate();
     }
     int64_t key = key_base;
-    for (int64_t value : values) {
+    for (int32_t value : values) {
       shared->Put(column_family, key, value, false /* pending */);
       ++key;
     }