Remove rubocop

[beccasaurus]

We keep disabling linting rules for these Ruby samples. See .rubocop.yml

Rubocop is a great tool for enforcing styles in Ruby libraries and applications.

For code samples, however, Rubocop has provided little to no benefit, while requiring configuration modifications frequently to disable more and more rules.

I favor the creation of a simple style guide, à la Github Ruby Style Guide, discussing our sample templates and style guidelines in addition to performing quality code reviews.

Adding this style guide is a high priority. In the meantime, however, I am going to remove Rubocop as a linting tool. The latest BigQuery sample that I've added has many false-positive violations causing me to disable many cops. Instead of continuing down that path, I am removing Rubocop.

This is done as a single commit, incase we want to revert for some reason in the future.

/cc @thagomizer