fix: update go-sdk reference to cleaned up commit

The upstream go-sdk PR was cleaned up based on reviewer feedback:
- Removed broken input validation optimization (ApplyDefaults on structs)
- Fixed sync.Map.Clear() usage
- Fixed benchmark naming

New commit 988974db6bfb contains only the schema caching optimization.

Author: SamMorrowDrums

go.mod

@@ -2,7 +2,7 @@ module github.com/github/github-mcp-server
 
 go 1.24.0
 
-replace github.com/modelcontextprotocol/go-sdk => github.com/SamMorrowDrums/go-sdk v0.0.0-20251204132233-46310a70a79a
+replace github.com/modelcontextprotocol/go-sdk => github.com/SamMorrowDrums/go-sdk v0.0.0-20251205102140-988974db6bfb
 
 require (
 	github.com/google/go-github/v79 v79.0.0