Remove nixops examples and documentation

examples/nixops/node.nix

@@ -1,5 +1,8 @@
+# This is an example network definition for deploying a nix-bitcoin node via NixOps.
+# NixOps deployment is currently untested.
+
 {
-  network.description = "Bitcoin Core node";
+  network.description = "Bitcoin node";
 
   bitcoin-node = { config, pkgs, lib, ... }: {
     imports = [
@@ -8,5 +11,9 @@
     ];
 
     nix-bitcoin.deployment.secretsDir = toString ../secrets;
+
+    #FIXME:
+    # Set `deployment.*` options like
+    # deployment.targetHost = "<address_or_hostname>";
   };
 }