DEV: Remove old redis option (#17427)

`Redis.exists_returns_integer` is now true by default

config/initializers/001-redis.rb

@@ -5,10 +5,6 @@ if Rails.env.development? && ENV['DISCOURSE_FLUSH_REDIS']
   Discourse.redis.flushdb
 end
 
-# Pending https://github.com/MiniProfiler/rack-mini-profiler/pull/450 and
-# upgrade to Sidekiq 6.1
-Redis.exists_returns_integer = true
-
 begin
   if Gem::Version.new(Discourse.redis.info['redis_version']) < Gem::Version.new("6.2.0")
     STDERR.puts "Discourse requires Redis 6.2.0 or up"