Rename local variable name `current_user` to `verified_user` [ci skip]

Assigning local variable named `current_user` in the condition is
confusing.

actioncable/README.md

@@ -53,8 +53,8 @@ module ApplicationCable
 
     private
       def find_verified_user
-        if current_user = User.find_by(id: cookies.signed[:user_id])
-          current_user
+        if verified_user = User.find_by(id: cookies.signed[:user_id])
+          verified_user
         else
           reject_unauthorized_connection
         end