It's definitely not the first time that tag's come up, and I've removed it once or twice myself.
I'll get it added to our tag blacklist. Specifically, we'll blacklist a tag that's composed just of number followed by an "e" (or "ed" or "edition").
I'm not inclined to synonymise it: other 5th editions exist, and since this isn't D&D Stack Exchange, our tags shouldn't be synonymised like that. If we instead blacklist it we can use this as a learning opportunity about our taxonomy, since blacklisted tags can come with information about what to do instead.
The blacklist request has been raised here: Blacklist #-edition tags