tests: re-enable tests that work

tests/test-sources/plugins/by-name/neotest/gtest.nix

@@ -1,8 +1,5 @@
-{ lib, pkgs, ... }:
 {
-  # TODO: added 2024-09-15
-  # TODO: Re-enable when upstream builds in darwin sandbox
-  example = lib.mkIf pkgs.stdenv.isLinux {
+  example = {
     # We cannot test neotest-gtest as it tries to create file in the upper directory
     # https://github.com/alfaix/neotest-gtest/blob/6e794ac91f4c347e2ea5ddeb23d594f8fc64f2a8/lua/neotest-gtest/utils.lua#L10-L16
     test.runNvim = false;