Remove CurrentUser.ip_addr.

Remove the `CurrentUser.ip_addr` global variable and replace it with
`request.remote_ip`. Before we had to track the current user's IP in a
global variable so that when we edited a post for example, we could pass
down the user's IP to the model and save it in the post_versions table.
Now that we now longer save IPs in version tables, we don't need a global
variable to get access to the current user's IP outside of controllers.

app/jobs/application_job.rb

@@ -11,7 +11,7 @@ class ApplicationJob < ActiveJob::Base
   queue_with_priority 0
 
   around_perform do |_job, block|
-    CurrentUser.scoped(User.system, "127.0.0.1") do
+    CurrentUser.scoped(User.system) do
       ApplicationRecord.without_timeout do
         Timeout.timeout(24.hours, JobTimeoutError) do
           block.call