fix previous typo
fix previous typo

Summary: old typos with FILTER/INDEX_CACHE

Test Plan: still pass this unit test

Reviewers: andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D61185

facebook/rocksdb,SunguckLee/RocksDB,hobinyoon/rocksdb,Andymic/rocksdb,OverlordQ/rocksdb,tsheasha/rocksdb,norton/rocksdb,Andymic/rocksdb,facebook/rocksdb,wat-ze-hex/rocksdb,tsheasha/rocksdb,hobinyoon/rocksdb,SunguckLee/RocksDB,Andymic/rocksdb,bbiao/rocksdb,tsheasha/rocksdb,OverlordQ/rocksdb,hobinyoon/rocksdb,vmx/rocksdb,wenduo/rocksdb,Andymic/rocksdb,hobinyoon/rocksdb,facebook/rocksdb,facebook/rocksdb,norton/rocksdb,OverlordQ/rocksdb,bbiao/rocksdb,tsheasha/rocksdb,norton/rocksdb,hobinyoon/rocksdb,vmx/rocksdb,hobinyoon/rocksdb,OverlordQ/rocksdb,wat-ze-hex/rocksdb,facebook/rocksdb,bbiao/rocksdb,wat-ze-hex/rocksdb,bbiao/rocksdb,hobinyoon/rocksdb,norton/rocksdb,tsheasha/rocksdb,norton/rocksdb,SunguckLee/RocksDB,facebook/rocksdb,wenduo/rocksdb,hobinyoon/rocksdb,OverlordQ/rocksdb,wenduo/rocksdb,wat-ze-hex/rocksdb,wat-ze-hex/rocksdb,vmx/rocksdb,wat-ze-hex/rocksdb,bbiao/rocksdb,Andymic/rocksdb,Andymic/rocksdb,vmx/rocksdb,tsheasha/rocksdb,norton/rocksdb,wenduo/rocksdb,Andymic/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,facebook/rocksdb,facebook/rocksdb,OverlordQ/rocksdb,wat-ze-hex/rocksdb,SunguckLee/RocksDB,vmx/rocksdb,SunguckLee/RocksDB,vmx/rocksdb,bbiao/rocksdb,norton/rocksdb,tsheasha/rocksdb,vmx/rocksdb,wat-ze-hex/rocksdb,norton/rocksdb,wenduo/rocksdb,tsheasha/rocksdb,wenduo/rocksdb,OverlordQ/rocksdb,wenduo/rocksdb,wenduo/rocksdb,SunguckLee/RocksDB,Andymic/rocksdb,SunguckLee/RocksDB,vmx/rocksdb