[now-ruby] Fix rails test (#3288)
[now-ruby] Fix rails test (#3288)

This test was failing for the last week.

The issue was fixed in the build environment. The root cause was [ruby-build](https://github.com/rbenv/ruby-build) which is used to install the version of Ruby used in `@now/ruby`. It started using an older (possible broken) version of `bundler`. I pinned `ruby-build` to a previous version so that deployments continue working.

So now we can enable the Rails test again (which uses nokogiri).

Fixes #3246
Closes #3274
zeit/now-cli,zeit/now-cli,zeit/now-cli,zeit/now-cli,zeit/now-cli,zeit/now-cli,zeit/now-cli