Guess I've never thought about what type of output this should be. It doesn't isn't a huge issue, but the scenario is this:

1. Developer submits TB add-on that lists support for TB21, but uses one of the removed bits of JS.
2. The message is raised, but it's only a notice.

A warning implies that something is wrong, while a notice implies that there's something that needs attention. Using JS that no longer exists is certainly something that's wrong.

Really, this just involves removing the `log_function` argument here and changing or removing [the `type_` argument up here](https://github.com/mozilla/amo-validator/pull/207/files#L0R14). Should only take a minute to change.