nixos/dnscrypt-proxy: remove

The upstream project ceased.

See https://github.com/NixOS/nixpkgs/issues/33540

nixos/tests/dnscrypt-proxy.nix

@@ -1,32 +0,0 @@
-import ./make-test.nix ({ pkgs, ... }: {
-  name = "dnscrypt-proxy";
-  meta = with pkgs.stdenv.lib.maintainers; {
-    maintainers = [ joachifm ];
-  };
-
-  nodes = {
-    # A client running the recommended setup: DNSCrypt proxy as a forwarder
-    # for a caching DNS client.
-    client =
-    { config, pkgs, ... }:
-    let localProxyPort = 43; in
-    {
-      security.apparmor.enable = true;
-
-      services.dnscrypt-proxy.enable = true;
-      services.dnscrypt-proxy.localPort = localProxyPort;
-      services.dnscrypt-proxy.extraArgs = [ "-X libdcplugin_example.so" ];
-
-      services.dnsmasq.enable = true;
-      services.dnsmasq.servers = [ "127.0.0.1#${toString localProxyPort}" ];
-    };
-  };
-
-  testScript = ''
-    $client->waitForUnit("dnsmasq");
-
-    # The daemon is socket activated; sending a single ping should activate it.
-    $client->execute("${pkgs.iputils}/bin/ping -c1 example.com");
-    $client->succeed("systemctl is-active dnscrypt-proxy");
-  '';
-})