Remove enableFastNegativeLookup from rocks

Summary: This flag will be removed from cachelib, as it was introduced for rollout purpose and is always true in production now.

Reviewed By: therealgymmy

Differential Revision: D51477965

fbshipit-source-id: 00d409c7c326e2eb9ed732d258da9962524c7206

cachelib/adaptor/rocks_secondary_cache/CachelibWrapper.cpp

@@ -270,7 +270,6 @@ std::unique_ptr<rocksdb::SecondaryCache> NewRocksCachelibWrapper(
         .setMaxWriteRate(opts.maxWriteRate)
         .setAdmWriteRate(opts.admissionWriteRate);
   }
-  nvmConfig.enableFastNegativeLookups = true;
 
   config.setCacheSize(opts.volatileSize)
       .setCacheName(opts.cacheName)