gopls/internal/mcp: unbreak build

Fix a broken build due to semantic merge conflict: mcp.NewTool was
renamed to mcp.NewServerTool.

Change-Id: I7de2c816b4241da4f21955b2f8888d70addf06df
Reviewed-on: https://go-review.googlesource.com/c/tools/+/682757
Reviewed-by: Hongxiang Jiang <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>
Reviewed-by: Junyang Shao <[email protected]>
Auto-Submit: Robert Findley <[email protected]>
TryBot-Bypass: Robert Findley <[email protected]>

Author: findleyr

gopls/internal/mcp/mcp.go

@@ -153,7 +153,7 @@ func newServer(session *cache.Session) *mcp.Server {
 				),
 			),
 		),
-		mcp.NewTool(
+		mcp.NewServerTool(
 			"diagnostics",
 			"Provide diagnostics for a region within a Go file",
 			func(ctx context.Context, _ *mcp.ServerSession, request *mcp.CallToolParamsFor[DiagnosticsParams]) (*mcp.CallToolResultFor[struct{}], error) {