fix bad implementation of ShardedCache::GetOccupancyCount (#11325)

Summary:
copy paste typo

Pull Request resolved: https://github.com/facebook/rocksdb/pull/11325

Reviewed By: hx235

Differential Revision: D44378512

Pulled By: ajkr

fbshipit-source-id: 509ed2697c06eed975914359ece0459a0ea40312

cache/sharded_cache.h

@@ -226,7 +226,7 @@ class ShardedCache : public ShardedCacheBase {
     return SumOverShards2(&CacheShard::GetPinnedUsage);
   }
   size_t GetOccupancyCount() const override {
-    return SumOverShards2(&CacheShard::GetPinnedUsage);
+    return SumOverShards2(&CacheShard::GetOccupancyCount);
   }
   size_t GetTableAddressCount() const override {
     return SumOverShards2(&CacheShard::GetTableAddressCount);