Fix worker validator

[victorfgs]

When setting a worker like so

# frozen_string_literal: true

class DemoJob

  include Sidekiq::Worker

  sidekiq_options queue: :low_priority,
                  lock: :until_and_while_executing,
                  on_conflict: {
                    client: :replace,
                    server: :raise,
                  }

  def perform(stub_id)
    p stub_id
  end
end

the rspec matcher passes because the get_sidekiq_options method returns something like

{
  "retry"=>3,
  "queue"=>:low_priority,
  "lock"=>:until_and_while_executing,
  "on_conflict"=>{ :client => :replace, :server => :raise }
}

since the on_conflict hash have symbol keys, the validator ends up returning valid.

This PR adds a check on the symbol keys just be sure we are checking the correct places.

Let me know if there's something else I can do to help in that fix :)