add threads:off to the config file

[ringabout]

Hello, Nim v2 is going to make threads:on default, which was discussed here: nim-lang/RFCs#361 and listed as the roadmap for 2.0: nim-lang/RFCs#437

I made a PR (nim-lang/Nim#19368) to enable threads, nitter gives in CI

  /Users/runner/work/Nim/Nim/pkgstemp/nitter/src/routes/preferences.nim(19, 10) template/generic instantiation of `router` from here
  /Users/runner/.nimble/pkgs/jester-0.5.0/jester.nim(1304, 35) template/generic instantiation of `async` from here
  /Users/runner/work/Nim/Nim/lib/pure/asyncmacro.nim(210, 31) Error: 'preferencesIter' is not GC-safe as it accesses 'defaultPrefs' which is a global using GC'ed memory

So I add threads:off to the config file.

[zedeus]

Thanks!