Fix mcp-server recipe: correct GitHub MCP server link and note upstream deprecation

[claudespice]

What the recipe said

mcp-server/README.md links the GitHub MCP server it proxies at:

https://github.com/modelcontextprotocol/servers/tree/main/src/github

What upstream did

The reference GitHub server was moved out of modelcontextprotocol/servers into modelcontextprotocol/servers-archived, so that tree URL now 404s:

$ curl -s -o /dev/null -w '%{http_code}' -L https://github.com/modelcontextprotocol/servers/tree/main/src/github
404
$ curl -s -o /dev/null -w '%{http_code}' -L https://github.com/modelcontextprotocol/servers-archived/tree/main/src/github
200

The npm package the recipe actually runs — spicepod.yaml sets mcp_args: -y @modelcontextprotocol/server-github — is correspondingly marked deprecated:

$ curl -s https://registry.npmjs.org/@modelcontextprotocol%2Fserver-github | jq -r '."dist-tags".latest, .versions[."dist-tags".latest].deprecated'
2025.4.8
Package no longer supported. Contact Support at https://www.npmjs.com/support for more info.

What changed

• Repointed the link to the archived location, which is where the code the recipe runs actually lives.
• Added a short note that the package is deprecated-but-functional, and that github/github-mcp-server is GitHub's supported replacement.

Deliberately left the spicepod.yaml alone. npx -y @modelcontextprotocol/server-github still resolves and runs — deprecated is not removed — so the recipe is not broken today, and migrating is not a like-for-like swap: github/github-mcp-server ships as a Go binary / Docker image rather than an npx package, so from: mcp:npx with mcp_args would need rethinking along with the github/* tool names in Steps 4–6. That is a maintainer call about the recipe's direction, not a mechanical accuracy fix — flagging it here rather than making it.

Verified against current stable Spice v2.1.1. Link checks are live; the recipe itself was not executed (needs a GitHub PAT).