This restores public access to recent changes, page history etc. which
was disabled in September 2019 due to misbehaving crawlers - see commits
https://github.com/archlinux/archwiki/commit/f2c518d3df94e9ad6898fdd03cac982902f8ac36
and https://github.com/archlinux/archwiki/commit/8595e8d66141e608db794f1deef3e52cb36e5e78.

Let's hope that our robots.txt has been improved since then and the
server load will not increase much. If it proves to be still a problem,
this commit can be reverted and we will figure out better solution.