Prioritise external nameserver on Tentacool first

Couldn't fetch the new Pi-hole image as-is.

hosts/tentacool/network.nix

@@ -5,11 +5,11 @@
     hostName = "tentacool";
 
     # This machine hosts Onix, the LAN nameserver. When the image is updated
-    # there needs to be another nameserver available in order to fetch the new
-    # image. An additional nameserver could be configured via DHCP, however
+    # there needs to be another nameserver prioritised in order to fetch the
+    # new image. An additional nameserver could be configured via DHCP, however
     # other devices have been spotted using this to workaround Onix, so DHCP
     # points only at Onix and this machine specifically will override DHCP's
-    # nameservers in order to configure this additional, external nameserver.
-    nameservers = [ "127.0.0.1" "8.8.8.8" ];
+    # nameservers in order to configure this external nameserver.
+    nameservers = [ "8.8.8.8" "127.0.0.1" ];
   };
 }