Fix callback to only run before update
Fix callback to only run before update

`before_save` doesn't accept `:on` as an argument, so this callback was actually running on all save events, not just on update.

https://github.com/rails/rails/issues/17622

Depending on what `reset_timestamp_attrs_for_update_if_needed` does, this might need to be backported to older versions.

I've submitted a PR to Rails to raise an exception when unexpected arguments are passed... unsure if an exception is the right way to go when there might be quite a few gems with this bug.

https://github.com/rails/rails/pull/30919
airblade/paper_trail,airblade/paper_trail,ifeelgoods/paper_trail,ifeelgoods/paper_trail