fixed typo in util/dynamic_bloom.h
fixed typo in util/dynamic_bloom.h

Summary:
fixed a typo in util/dynamic_bloom.h
Closes https://github.com/facebook/rocksdb/pull/2442

Differential Revision: D5242397

Pulled By: IslamAbdelRahman

fbshipit-source-id: c47fd18cc79afff6b022201a0410c0cd47626576

bbiao/rocksdb,Andymic/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,Andymic/rocksdb,Andymic/rocksdb,bbiao/rocksdb,Andymic/rocksdb,SunguckLee/RocksDB,Andymic/rocksdb,Andymic/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,Andymic/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,bbiao/rocksdb,Andymic/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb