chore (continuwuity, continuwuity-nightly): use foregejo update functions

[julian45]

FyraLabs/anda#472 adds Forgejo-specific update functions, and these packages can take advantage of forgejo and forgejo_commit, so let's use those!

[Owen-sz]

This is a working nightly update script:

rpm.global("commit", forgejo_commit("forgejo.ellis.link", "continuwuation/continuwuity"));
if rpm.changed() {
  rpm.release();
  rpm.global("commit_date", date());
}

[Owen-sz]

Stable tested working