Remove `GITLAB_ENABLE_QUERY_ANALYZERS` feature flag

The query analyzers feature is already fully rolled out
to the production.

It is safe to remove this to simplify rollout.

config/initializers/database_query_analyzers.rb

 # frozen_string_literal: true
 
 # Currently we register validator only for `dev` or `test` environment
-if Gitlab.dev_or_test_env? || Gitlab::Utils.to_boolean(ENV['GITLAB_ENABLE_QUERY_ANALYZERS'], default: false)
-  Gitlab::Database::QueryAnalyzer.instance.hook!
-  Gitlab::Database::QueryAnalyzer.instance.all_analyzers.append(::Gitlab::Database::QueryAnalyzers::GitlabSchemasMetrics)
+Gitlab::Database::QueryAnalyzer.instance.hook!
+Gitlab::Database::QueryAnalyzer.instance.all_analyzers.append(::Gitlab::Database::QueryAnalyzers::GitlabSchemasMetrics)
 
-  if Rails.env.test? || Gitlab::Utils.to_boolean(ENV['ENABLE_CROSS_DATABASE_MODIFICATION_DETECTION'], default: false)
-    Gitlab::Database::QueryAnalyzer.instance.all_analyzers.append(::Gitlab::Database::QueryAnalyzers::PreventCrossDatabaseModification)
-  end
+if Rails.env.test? || Gitlab::Utils.to_boolean(ENV['ENABLE_CROSS_DATABASE_MODIFICATION_DETECTION'], default: false)
+  Gitlab::Database::QueryAnalyzer.instance.all_analyzers.append(::Gitlab::Database::QueryAnalyzers::PreventCrossDatabaseModification)
+end
 
-  Gitlab::Application.configure do |config|
-    config.middleware.use(Gitlab::Middleware::QueryAnalyzer)
-  end
+Gitlab::Application.configure do |config|
+  config.middleware.use(Gitlab::Middleware::QueryAnalyzer)
 end

lib/gitlab/sidekiq_middleware.rb

@@ -33,7 +33,7 @@ module Gitlab
         chain.add ::Gitlab::SidekiqMiddleware::BatchLoader
         chain.add ::Gitlab::SidekiqMiddleware::InstrumentationLogger
         chain.add ::Gitlab::SidekiqMiddleware::AdminMode::Server
-        chain.add ::Gitlab::SidekiqMiddleware::QueryAnalyzer if Gitlab.dev_or_test_env? || Gitlab::Utils.to_boolean(ENV['GITLAB_ENABLE_QUERY_ANALYZERS'], default: false)
+        chain.add ::Gitlab::SidekiqMiddleware::QueryAnalyzer
         chain.add ::Gitlab::SidekiqVersioning::Middleware
         chain.add ::Gitlab::SidekiqStatus::ServerMiddleware
         chain.add ::Gitlab::SidekiqMiddleware::WorkerContext::Server