Comment typo

Summary: Closes https://github.com/facebook/rocksdb/pull/3546

Differential Revision: D7111708

Pulled By: ajkr

fbshipit-source-id: 522a4a00eb3e34c73afcb86c1f75cd2e90e7608d

db/db_impl.h

@@ -1367,7 +1367,7 @@ class DBImpl : public DB {
     return Env::WLTH_SHORT;
   }
 
-  // When set, we use a seprate queue for writes that dont write to memtable. In
+  // When set, we use a separate queue for writes that dont write to memtable. In
   // 2PC these are the writes at Prepare phase.
   const bool two_write_queues_;
   const bool manual_wal_flush_;