Remove `Dependency` section form README

This module doesn’t require any dependencies, because it downloads [the binaries of jpeg-recompress](https://github.com/1000ch/node-jpeg-recompress-bin/tree/master/vendor) directly, instead of building from source.
Actually, [the test on Travis CI](https://travis-ci.org/1000ch/node-jpeg-recompress-bin/builds/32392623) passes without pre-installing any dependencies.