Switch from i3-gaps to i3 due to merge

hosts/desktop.nix

@@ -22,10 +22,7 @@
         };
         defaultSession = "none+i3";
       };
-      windowManager.i3 = {
-        enable = true;
-        package = pkgs.i3-gaps;
-      };
+      windowManager.i3.enable = true;
     };
   };