Remove all redirects that are a year old or older

As part of the monthly chores, I realized it's now been a year since we first implemented the server-side redirects, and it's time to start cleaning up the old ones that are only intended to stay for one year.

We'll need to make some kind of automated (or Manual to start) process to do this every month, but for this first month, since it's so big (and I'm the one that put them in there in the first place), I did it manually.

Related to technical-writing#514 (closed)