Fix C4702 on windows (#10146)

Summary:
This code is unreachable when `ROCKSDB_LITE` not defined. And it cause build fail on my environment VS2019 16.11.15.
```
-- Selecting Windows SDK version 10.0.19041.0 to target Windows 10.0.19044.
-- The CXX compiler identification is MSVC 19.29.30145.0
-- The C compiler identification is MSVC 19.29.30145.0
-- The ASM compiler identification is MSVC
```

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10146

Reviewed By: akankshamahajan15

Differential Revision: D37112916

Pulled By: ajkr

fbshipit-source-id: e0b2bf3055d6fac1b3fb40b9f02c4cbae3f82757

db/db_impl/db_impl.cc

@@ -812,8 +812,9 @@ Status DBImpl::StartPeriodicWorkScheduler() {
   return periodic_work_scheduler_->Register(
       this, mutable_db_options_.stats_dump_period_sec,
       mutable_db_options_.stats_persist_period_sec);
-#endif  // !ROCKSDB_LITE
+#else
   return Status::OK();
+#endif  // !ROCKSDB_LITE
 }
 
 // esitmate the total size of stats_history_