services/barrier: drop module

Upstream package removed and unmaintained project. Recommended to
replace with maintained alternatives such as `deskflow` and `input-leap`

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

tests/modules/services/barrier/basic-configuration.nix

@@ -1,13 +0,0 @@
-{
-  services.barrier.client = {
-    enable = true;
-    server = "testServer";
-  };
-
-  nmt.script = ''
-    clientServiceFile=home-files/.config/systemd/user/barrierc.service
-
-    assertFileExists $clientServiceFile
-    assertFileRegex $clientServiceFile 'ExecStart=.*/bin/barrierc -f testServer'
-  '';
-}

tests/modules/services/barrier/default.nix

@@ -1,5 +0,0 @@
-{ lib, pkgs, ... }:
-
-lib.optionalAttrs pkgs.stdenv.hostPlatform.isLinux {
-  barrier-basic-configuration = ./basic-configuration.nix;
-}