private/model/api: Fix pagination helper method doc example

Fixes the pagination helper method's doc example to refer to the package
of the paginator.

Fix aws#2374

private/model/api/operation.go

@@ -307,7 +307,7 @@ func (c *{{ .API.StructName }}) {{ .ExportedName }}WithContext(` +
 //    // Example iterating over at most 3 pages of a {{ .ExportedName }} operation.
 //    pageNum := 0
 //    err := client.{{ .ExportedName }}Pages(params,
-//        func(page {{ .OutputRef.GoType }}, lastPage bool) bool {
+//        func(page {{ .OutputRef.Shape.GoTypeWithPkgName }}, lastPage bool) bool {
 //            pageNum++
 //            fmt.Println(page)
 //            return pageNum <= 3