Revert "Merge branch 'check_pg_stat_activity' into 'master'"

This reverts merge request !25723

spec/support/pg_stat_activity.rb

-# frozen_string_literal: true
-
-RSpec.configure do |config|
-  config.before do
-    if Gitlab::Database.postgresql? && ENV['PG_STAT_WARNING_THRESHOLD']
-      warning_threshold = ENV['PG_STAT_WARNING_THRESHOLD'].to_i
-      results = ActiveRecord::Base.connection.execute('SELECT * FROM pg_stat_activity')
-      ntuples = results.ntuples
-
-      warn("pg_stat_activity count: #{ntuples}")
-
-      if ntuples > warning_threshold
-        results.each do |result|
-          warn result.inspect
-        end
-      end
-    end
-  end
-end