Revert "Fix the SQLite gem name"

This reverts commit 700c6c65bcce17d4c61423ceaef031bcbe203337.

Bot the `sqlite3` and `sqlite3-ruby` gems exist.
https://rubygems.org/gems/sqlite3
https://rubygems.org/gems/sqlite3-ruby

In fact, they both point to the same github repository.
https://github.com/luislavena/sqlite3-ruby

However, the last one hasn't been released since 2011, while the first
one keeps getting regular releases.