re-enable nightly Windows 6.2.1 CI

Author: matthewbastien

.github/workflows/nightly.yml

@@ -114,5 +114,3 @@ jobs:
       windows_pre_build_command: . .github\workflows\scripts\windows\setup.ps1
       windows_build_command: Invoke-Program scripts\test_windows.ps1
       enable_windows_docker: false
-      # TODO re-enable when 6.2.1 toolchain working
-      enable_windows_checks: false