Fix Credo code readability issues

lib/web/email/checker.ex

@@ -3,8 +3,7 @@ defmodule Mobilizon.Web.Email.Checker do
   Provides a function to test emails against a "not so bad" regex.
   """
 
-  # TODO: simplify me!
-  @email_regex ~r/^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/
+  @email_regex ~r/^[\w.!#$%&’*+\-\/=?\^`{|}~]+@[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)*$/i
 
   @doc """
   Returns whether the email is valid.