Change Redis#exists calls to Redis#exists? to avoid deprecation warning (#14191)

config/application.rb

@@ -7,6 +7,7 @@ require 'rails/all'
 Bundler.require(*Rails.groups)
 
 require_relative '../app/lib/exceptions'
+require_relative '../lib/redis/namespace_extensions'
 require_relative '../lib/paperclip/url_generator_extensions'
 require_relative '../lib/paperclip/attachment_extensions'
 require_relative '../lib/paperclip/media_type_spoof_detector_extensions'

config/initializers/redis.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-Redis.exists_returns_integer = false
-
 redis_connection = Redis.new(
   url: ENV['REDIS_URL'],
   driver: :hiredis