nixos/tests/haproxy: stop using nixos/profiles/minimal

The defaults conflicts with the defaults of `services.httpd`:
```
error: The option `nodes.machine.services.logrotate.enable' has conflicting definition values:
       - In `/home/thomas/Workspace/Packaging/nixpkgs/nixos/modules/profiles/minimal.nix': false
       - In `/home/thomas/Workspace/Packaging/nixpkgs/nixos/modules/services/web-servers/apache-httpd/default.nix': true
       Use `lib.mkForce value` or `lib.mkDefault value` to change the priority on any of these definitions.
(use '--show-trace' to show detailed location information)
```

`nixos/profile/minimal` is not used in the majority of the tests and it does not
seem to have a specific reason to use it for the HAProxy test.

nixos/tests/haproxy.nix

@@ -2,7 +2,6 @@ import ./make-test-python.nix ({ pkgs, ...}: {
   name = "haproxy";
   nodes = {
     machine = { ... }: {
-      imports = [ ../modules/profiles/minimal.nix ];
       services.haproxy = {
         enable = true;
         config = ''