ci: run the bump workflow on Gitea Actions

The tap moved to git.trivk.dev. Gitea Runner has no parallel steps, so
the two bumps run one after the other. The scripts ask api.github.com
with curl instead of gh, which needs a GitHub token the Gitea job does
not have; two unauthenticated requests per run stay far under the limit.
The README now taps with the git.trivk.dev URL.

.github/scripts/bump-zshellcheck.sh

@@ -4,7 +4,7 @@
 set -euo pipefail
 formula=Formula/zshellcheck.rb
 repo=afadesigns/zshellcheck
-latest=$(gh api repos/$repo/releases/latest --jq .tag_name)
+latest=$(curl -fsSL "https://api.github.com/repos/$repo/releases/latest" | jq -r .tag_name)
 latest=${latest#v}
 current=$(sed -nE 's|.*/releases/download/v([^/]+)/.*|\1|p' "$formula" | head -1)
 if [ "$latest" = "$current" ]; then