nixos/tests/gitea: fix

* Since Gitea 1.20 the request to `/commits` requires at least one retry
  because it appears to take a moment until Gitea actually knows that
  this repo isn't empty anymore (previously on 1.20 this failed with
  HTTP 409 which occurs when the requested repo is empty).
* Remove `*.shutdown()`, for some reason they hang regularly for unknown
  reasons.

nixos/tests/gitea.nix

@@ -121,14 +121,10 @@ let
       client2.succeed(f"GIT_SSH_COMMAND='{GIT_SSH_COMMAND}' git clone {REPO}")
       client2.succeed('test "$(cat repo/testfile | xargs echo -n)" = "hello world"')
 
-      server.succeed(
+      server.wait_until_succeeds(
           'test "$(curl http://localhost:3000/api/v1/repos/test/repo/commits '
           + '-H "Accept: application/json" | jq length)" = "1"'
       )
-
-      client1.shutdown()
-      client2.shutdown()
-      server.shutdown()
     '';
   });
 in