feeds: document Metaculus Journal

hosts/common/feeds.nix

@@ -1,6 +1,8 @@
 # candidates:
 # - The Nonlinear Library (podcast): <https://forum.effectivealtruism.org/posts/JTZTBienqWEAjGDRv/listen-to-more-ea-content-with-the-nonlinear-library>
 #   - has ~10 posts per day, text-to-speech; i would need better tagging before adding this
+# - <https://www.metaculus.com/questions/11102/introducing-the-metaculus-journal-podcast/>
+#   - dead since 2022/10 - 2023/03
 
 { lib, sane-data, ... }:
 let