rocksdb: change target-file-size-base back to 8M (#8918)
rocksdb: change target-file-size-base back to 8M (#8918)

Signed-off-by: Yi Wu <bc6ae85de42d744f2dc8adc7731d42b35611b18f@pingcap.com>
pingcap/tikv,BusyJay/tikv,pingcap/tikv,c4pt0r/tikv,BusyJay/tikv,BusyJay/tikv,BusyJay/tikv