Don't use update_attribute

This method is ambiguous. Sometimes we use it to set invalid data in
tests (which can usually be done with `update_column`), and other times
we use it instead of `update!`.

I'm removing it because, even if sometimes it could make sense to use
it, it's too similar to `update_attributes` (which is an alias for
`update` and runs validations), making it confusing.

However, there's one case where we're still using it: in the
ActsAsParanoidAliases module, we need to invoke the callbacks, which
`update_column` skips, but tests related to translations fail if we use
`update!`. The reason for this is the tests check what happens if we
restore a record without restoring its translations. But that will make
the record invalid, since there's a validation rule checking it has at
least one translation.

I'm not blacklisting any other method which skips validations because we
know they skip validations and use them anyway (hopefully with care).

spec/controllers/comments_controller_spec.rb

@@ -27,7 +27,7 @@ describe CommentsController do
 
     it "does not create a comment if the comments are closed" do
       sign_in user
-      legal_process.update_attribute(:debate_end_date, Date.current - 1.day)
+      legal_process.update!(debate_end_date: Date.current - 1.day)
 
       expect do
         post :create, xhr: true,