Summary:
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8208
Make include of "file_system.h" use the same include path as everywhere
else.
Reviewed By: riversand963, akankshamahajan15
Differential Revision: D27881606
fbshipit-source-id: fc1e076229fde21041a813c655ce017b5070c8b3