Enable `Lint/EmptyBlock`

[cocoahero]

Hopefully a straight-forward proposal to enable Lint/EmptyBlock, in an effort to prevent situations like this:

field :my_graphql_field, :string, null: true do |f|
  # something was here but removed by rudimentary automation
end

[rafaelfranca]

I'm pretty sure I didn't enable this because of legit reasons. I need to run against our codebase to check.