CoC: Fix wiki link in "About this document"

code-of-conduct.md:
Fix the wiki link to the historic version of the Code of Conduct in the
"About this document" section.
The location changed due to hosting the "General guidelines" (i.e.
technical guidelines) on the Arch wiki again.

code-of-conduct.md

@@ -244,8 +244,8 @@ may occur outside of the 30 days notice period for changes to the Code of Conduc
 ## About this document
 
 This code of conduct has been originally developed on the Arch wiki, where [its history](
-https://wiki.archlinux.org/index.php?title=Code_of_conduct&action=history) can be found. Later
-revisions of this document can be found in the [Arch Linux Service Agreements](
+https://wiki.archlinux.org/index.php?oldid=648541&date-range-to=2021-01-09&action=history) can be
+found. Later revisions of this document can be found in the [Arch Linux Service Agreements](
 https://gitlab.archlinux.org/archlinux/service-agreements) repository.
 
 The text is available under the terms of the [GNU Free Documentation License 1.3 or later](