False positive for ActionControllerFlashBeforeRender when render and redirect_to are both present

[chris-hewitt]

ActionControllerFlashBeforeRender also triggers when flash[] comes after render. This causes a false positive for a scenario such as:

    render :index and return if foo
    flash[:alert] = "msg"
    redirect_to "https://www.example.com/"

(It looks the cop's followed_by_render? method currently behaves more like a sibling_of_render?)

---

Expected behavior

0 failures

Actual behavior

Offenses:

[Correctable] Rails/ActionControllerFlashBeforeRender: Use flash.now before render.
    flash[:alert] = "msg"
    ^^^^^

Steps to reproduce the problem

RSpec.describe RuboCop::Cop::Rails::ActionControllerFlashBeforeRender, :config do
  ...
  context 'when using `flash` before `redirect_to`' do
    ...
    context 'when `render` is also present earlier in the method' do
      it 'does not register an offense' do # <-- FAILS
        expect_no_offenses(<<~RUBY)
          class HomeController < ApplicationController
            def create
              render :index and return unless foo
              flash[:alert] = "msg"
              redirect_to "https://www.example.com/"
            end
          end
        RUBY
      end
    end
end

RuboCop version

$ bundle exec rubocop -V
1.36.0 (using Parser 3.1.2.1, rubocop-ast 1.21.0, running on ruby 2.7.6) [x86_64-linux]
  - rubocop-performance 1.15.0
  - rubocop-rails 2.16.1
  - rubocop-rspec 2.13.2