radicle-node: fix update script

- only update to stable releases
- sort git tags to find the latest version

pkgs/by-name/ra/radicle-node/update.sh

···
 #!/usr/bin/env nix-shell
-#!nix-shell -i bash -p coreutils gnused common-updater-scripts nix-update
+#!nix-shell -i bash -p coreutils gnugrep common-updater-scripts nix-update
 
-version=$(list-git-tags | tail -1 | sed 's|^releases/||')
+version=$(list-git-tags | grep -oP '^releases/\K\d+\.\d+\.\d+$' | sort -rV | head -1)
 nix-update --version="$version" radicle-node