Fix protocol version in Versioning page (modelcontextprotocol#1910)

This updates the current protocol version link text to match the URL,
and uses the `/specification/latest` wildcard redirect for the
initialization phase link.

Co-authored-by: David Soria Parra <[email protected]>

Author: jonathanhefner

docs/specification/versioning.mdx

@@ -29,7 +29,7 @@ The **current** protocol version is [**2025-11-25**](/specification/2025-11-25/)
 ## Negotiation
 
 Version negotiation happens during
-[initialization](/specification/2025-11-25/basic/lifecycle#initialization). Clients and
+[initialization](/specification/latest/basic/lifecycle#initialization). Clients and
 servers **MAY** support multiple protocol versions simultaneously, but they **MUST**
 agree on a single version to use for the session.