[Misc] Remove elasticsearch-rails gem

There is no counterpart for OpenSearch.
`elasticsearch-model` needs to go too but that is more involved than
just removing something that only facilitates logging in dev.

This was responsible for
* displaying the time elasticsearch queries took per request
* logging the search parameters being sent to elasticsearch per query

The implementation isn't that complex and I could roll something myself but
considering that I haven't sought that information out by now I'll just don't.
Logging queries is trivial since we craft these manually ourselves.

Gemfile

@@ -30,7 +30,6 @@ gem 'redis'
 gem 'request_store'
 
 gem 'elasticsearch-model'
-gem 'elasticsearch-rails'
 
 gem 'mailgun-ruby'
 gem 'resolv'

Gemfile.lock

@@ -134,7 +134,6 @@ GEM
       activesupport (> 3)
       elasticsearch (~> 7)
       hashie
-    elasticsearch-rails (7.2.1)
     elasticsearch-transport (7.17.7)
       faraday (~> 1)
       multi_json
@@ -408,7 +407,6 @@ DEPENDENCIES
   draper
   dtext_rb!
   elasticsearch-model
-  elasticsearch-rails
   factory_bot_rails
   httparty
   listen

config/application.rb

@@ -21,8 +21,6 @@ Bundler.require(*Rails.groups)
 require_relative "danbooru_default_config"
 require_relative "danbooru_local_config"
 
-require 'elasticsearch/rails/instrumentation'
-
 module Danbooru
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.