Remove SubjectToFirewall

This tag is badly documented -- wrongly as "SubjectToFirestorm" and only mentioned in some sidenote -- and generally confusing considering there's IgnoresFirestorm already, which exactly the same purpose. It might have been added to separate new and original logics, but it's unintuitive that one would be used for projectiles and the other for technos and projectiles.

The tag should be removed, and IgnoresFirestorm be used instead.