Remove zfs from busch btrfs raid and add zramswap

btrfs doesn't allow having swap subvol on raid devices.

hosts/busch/default.nix

@@ -71,6 +71,11 @@
     };
   };
 
+  zramSwap = {
+    enable = true;
+    memoryPercent = 50;
+  };
+
   networking.useDHCP = false;
 
   systemd.network = {

hosts/busch/disko.nix

@@ -91,10 +91,6 @@
                       mountOptions = [ "compress=zstd" ];
                       mountpoint = "/var/lib/pve-cluster";
                     };
-                    "/swap" = {
-                      mountpoint = "/.swapvol";
-                      swap.swapfile.size = "32G";
-                    };
                   };
                 };
               };