n8n: auto update to highest stable version

Previously it updated to the version that GitHub marked as latest, but
this could be a few versions behind sometimes.

pkgs/by-name/n8/n8n/update.sh

@@ -2,5 +2,6 @@
 #!nix-shell --pure -i bash -p bash curl jq nix-update cacert git
 set -euo pipefail
 
-new_version="$(curl -s "https://api.github.com/repos/n8n-io/n8n/releases/latest" | jq --raw-output '.tag_name | ltrimstr("n8n@")')"
+new_version="$(curl -s "https://api.github.com/repos/n8n-io/n8n/releases?per_page=30" | \
+  jq --raw-output 'map(select(.prerelease | not) | .tag_name) | sort | last | ltrimstr("n8n@")')"
 nix-update n8n --version "$new_version"