Fix 404 links in v1 README to renamed example files by jerome3o-anthropic · Pull Request #2822 · modelcontextprotocol/python-sdk

The v1 README (frozen on main) links to examples/snippets/servers/
fastmcp_quickstart.py and examples/fastmcp/icons_demo.py on the main
branch, but those files were renamed there as part of the FastMCP ->
MCPServer rename, so both links now 404. Point them at the v1.x
branch, where the files still exist and match the documented v1 API.

The remaining example links still resolved on main, but the files there
were rewritten for v2 (FastMCP -> MCPServer), so they showed code that
no longer matches the v1 API this README documents. Point every example
link at v1.x, matching the two 404 fixes. The LICENSE link stays on
main; the file is identical on both branches.

Committed with SKIP=readme-v1-frozen like the previous commit.