chore: remove whitby configuration

Removes whitby DNS records and other related configuration that is no longer
required now that whitby is gone.

whitby served us well. RIP.

This resolves b/433.

Change-Id: I56fe6f88cde9112fc3bfc79758ac33e88a743422
Reviewed-on: https://cl.tvl.fyi/c/depot/+/13117
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>

ops/modules/www/cache.tvl.fyi.nix

@@ -6,6 +6,9 @@ let
   # This attrset forms a linked list of hosts, which delegate ACME fallbacks to
   # each other. These *must* form a circle, otherwise we may end up walking only
   # part of the ring.
+  #
+  # TODO: remove whitby from here, it is gone; leaving this code for now for
+  # easier discovery when reconfiguring this.
   acmeFallback = host: ({
     whitby = "nevsky.cache.tvl.fyi";
     nevsky = "whitby.cache.tvl.fyi"; # GOTO 1
@@ -26,7 +29,9 @@ in
       # hosts. This config is kind of messy; it would be nice to generate a
       # correct ring from the depot fixpoint, but this may be impossible due to
       # infinite recursion. Please read the comment on `acmeFallback` above.
-      acmeFallbackHost = acmeFallback config.networking.hostName;
+      #
+      # TODO: whitby is gone, this is not needed at the moment
+      # acmeFallbackHost = acmeFallback config.networking.hostName;
 
       extraConfig = ''
         location = /cache-key.pub {