Correct ruby syntax highlight

Github is a know user of the pygments on their backend server: https://github.com/toptal/chewy/blob/master/lib/chewy/rspec/update_index.rb

The problem starts around line 189, looks like the first right curly brace closes the string interpolation too soon.

  failure_message_when_negated do
    if @updated.any?
      "Expected index `#{type_name}` not to be updated, but it was with #{
        @updated.map(&:values).flatten.group_by { |documents| documents[:_id] }.map do |id, documents|
          "\n  document id `#{id}` (#{documents.count} times)"
        end.join
      }\n"
    end
  end

RubyLexer: Keep state with nested interpolations

Fixes #1018

→ <<cset a8918c870266>>