Summary:
The SST file sizes changed slightly after the improvement of PR #3970
which reduces the size of the properties block. Before PR #3970 a size
ratio compaction included all of the first four flushed files but it
only includes two files after. We increase the size_ratio universal
compaction option to make that compaction include all four files again.
Closes https://github.com/facebook/rocksdb/pull/3995

Differential Revision: D8426925

Pulled By: fgwu

fbshipit-source-id: 1429c38672e9f4fb4d4881fd4b06db45c4861d62